Controlled-gradient, accelerated-vapor-recompression apparatus and method

ABSTRACT

An accelerated vapor recompression apparatus  10  converts incoming flow  35   a  to a concentrate  35   c  by developing a concentration profile  146  within a tank  30  holding a liquid  23  containing dissolved solids. The resulting curve  160  of saturation temperature of the stratified liquid  23  (such as a brine  23  or other material  23 ) moves away from the curve  162  corresponding to fully mixed conditions. The shift  174, 180  in saturation temperature results in increased boiling without increased energy from a heater  70  or compressor  50 . A method  90, 200  of control of the system provides interventions  203, 204, 205, 206  at different levels  92, 94, 96, 98  of control, ranging from mass flows  35  to work of a compressor  50 , heat from a heater  70 , and a predictive processing  215  of feedback  217  for controlling commands  216  algorithmically.

RELATED APPLICATIONS

This application: claims the benefit of co-pending U.S. ProvisionalPatent Application Ser. No. 61/594,285, filed Feb. 2, 2012; is acontinuation in part of co-pending U.S. patent application Ser. No.13/372,182, filed on Feb. 13, 2012, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/443,245, filed on Feb. 15,2011; is a continuation in part of co-pending U.S. patent applicationSer. No. 12/687,753, filed on Jan. 14, 2010, which claims the benefit ofU.S. Provisional Patent Application Ser. No. 61/144,694, filed on Jan.14, 2009; is a continuation in part of co-pending U.S. patentapplication Ser. No. 12/687,746, filed on Jan. 14, 2010, which claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/144,665,filed on Jan. 14, 2009; is a continuation in part of co-pending U.S.patent application Ser. No. 13/372,232, filed on Feb. 13, 2012, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.61/443,245, filed on Feb. 15, 2011; and is a continuation in part ofco-pending U.S. patent application Ser. No. 13/372,276, filed on Feb.13, 2012, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/443,245, filed on Feb. 15, 2011; all of whichare herein incorporated by reference in their entirety.

BACKGROUND

1. The Field of the Invention

This invention relates to heat transfer and, more particularly, to novelsystems and methods for vapor recompression.

2. The Background Art

Heat recovery is the basis of electrical co-generation plants Likewisemany food and beverage processes require heat recovery for economy.Meanwhile, desalination plants, sugar processing, distillation systems,and the like rely on recovery of latent heat in order to minimize netenergy requirements. Heat may be recovered by reheating, pre-heating, orotherwise exchanging heat from an exit flow into and incoming flowthrough a system of heat exchangers.

Vapor recompression is used in various forms as one method for heatrecovery. For example, in food processing, industrial waste processing,oil production brine processing, and the like, vapor recompressionrelies on conventional heat exchangers and technologies to exchangeheat, vaporize liquids, and condense distillates. The chemicalconstitution of dissolved materials, especially dissolved solids, aswell as various ions and the like take a toll in energy and damage tothe processing equipment for energy exchange.

For example, oil production results in pumping considerable water to thesurface. That water often contains some amount of hydrocarbons, salts,methane, ammonia, trace elements, or a combination thereof. Thereforethe water cannot be released into other water flows without treatment.Meanwhile, disposal by hauling, followed by re-injection, or evaporationby ponds or boilers, is expensive.

Industrial waste, distillation process in food and beverage industriesand the like have similar, if not always so severe, problems. Even thelatest methods such as vapor recompression and multiple-effectdistillation struggle with efficiency, energy budgets, and equipmentmaintenance in the face of corrosion, fouling, scaling, and so forth.Better systems are needed for heat recovery and re-use.

SUMMARY OF THE INVENTION

In view of the foregoing, in accordance with the invention as embodiedand broadly described herein, a method and apparatus are disclosed inone embodiment of the present invention as including a controlledgradient of a material, such as, for example, total dissolved solids(TDS) in a boiling liquid column, such as a brine. Adjacent columnscontain condensing vapors at an increased pressure. High heat transfercoefficients and effective stratified densification of the liquid areobtained by controlling mass flows, work, heat and the like, and sensingand controlling predictively based on balancing mass, work, energy, andthe rates of change thereof, include rates of change in the rates ofchange (second derivatives of values).

In one embodiment of the method in accordance with the invention, asystem may operate by providing a feed comprising a liquid containing afirst material, distinct from the liquid and dissolved therein, andcontaining the feed as a pool. A core at least partially immersed in thepool may be in thermal communication therewith and sealed against directfluid communication therewith.

One may create a concentration profile reflecting a variation of theconcentration of the first material in the pool between a liquid levelat the top thereof and the bottom thereof by recycling vapor produced inthe pool into a condensate within the core. Typically, a containercontaining the feed is selected from a pond, a tank, an estuary, and avessel, and the pool is quiescent relative to the feed.

The core may further comprise closed channels in thermal communicationwith the pool, in indirect fluid communication therewith, and sealedagainst direct fluid communication therewith, which may be oriented toflow the vapor and condensate in a vertical direction. Controllingaccretion of compositions containing the first material may be done byselecting the attitude of the core in operation.

The portion of the pool within the core may be engaged in confinedboiling, and the profile (which may be thought of as gradient, but isnot necessarily monotonic or linear) is effected by establishing anexchange of heat from the core into the pool. A change in phase of theliquid within the core, by confinement therein vaporizes the liquidduring the heat transfer from the core.

Optimizing the concentration profile may be done by providing aplurality of panels and selecting a spacing therebetween for enclosingtherebetween, in at least two dimensions, a portion of the pool. Forexample, this may include providing a plurality of panels and selectinga spacing therebetween for enclosing therebetween, in at least twodimensions, a portion of the pool. Spacing may be based on thecharacteristics of the feed.

The method may include selecting at least one of a spacing betweenpanels of the plurality of panels, a number of the panels in the core, asize of the panels, material of the core, attitude of the core, othercharacteristics of the panels, and the position of the core in the pool,and a combination thereof based on the characteristics of the feed.

Operation of the system and method establishes an active regionproximate the core and containing a substantial majority of thevariation in the concentration profile, and establishes a trap regionbelow the active region, which is substantially excluded from exchangingliquid into the active region.

Optimizing heat transfer may be done by fully immersing the core intothe pool, and controlling or changing an effective nucleate boilingregion of the core by changing the concentration profile. Changing atemperature profile in the pool by adding heat corresponding to a changein a pressure above the pool may be done, and may be balanced with workby the compressor to obtain stability at a set of conditions desired.

In one embodiment of a method in accordance with the invention, aprocess may include changing a temperature profile in the first regionby adding heat based on a change in a pressure above the first region.Changing a boiling region of the core may be effected by changing theconcentration profile, which may be used to change the effectivesaturation temperature, pressure, or both for the liquid. The pool maybe quiescent relative to the feed, meaning that flows are generallycomparatively slower, with turbulence only local, and not general.

One embodiment of an apparatus in accordance with the invention, mayinclude a containment means adapted for receiving a feed comprising aliquid containing a first material distinct from the liquid anddissolved therein. The containment means may be configured to contain acollection of the feeds as a pool having a liquid level and a bottomlevel. A core may be at least partially immersed in the pool to be inthermal communication therewith and sealed against direct fluidcommunication therewith.

Means for processing the pool may create a concentration profilereflecting a variation in concentration of the first material in thepool between the liquid level and the bottom. This processing means mayfurther comprise compression means recycling vapor produced in the poolinto a condensate within the core, and may include heating means (suchas a heater, for example) for adding thermal energy into the pool. Theprocessing means may include a compressor, which is one embodiment of arecycling means for recycling vapor produced in the pool into acondensate within the core.

Containment means may be selected from a pond, a tank, an estuary, avessel, or the like. The core may include closed channels in thermalcommunication with the pool, in indirect fluid communication therewith(e.g. to receive vapor), and sealed against direct fluid communicationtherewith. The core may be movable, for moving relative to thecontainment means. When the core is engaged in confined boiling, movingmay be used to adjust spacing between panels of the core. Moving thecore may include changing the orientation of it, changing a spacingbetween the closed channels, or the like.

In one embodiment of an apparatus in accordance with the invention,configured as a heat exchanger suitable for use in a medium configuredas a fluid, the heat exchanger may include an inlet, outlet, andsurfaces. Surfaces may include an exterior surface and an interiorsurface, defining an interior volume in fluid communication with theinlet and the outlet.

The surfaces may be constructed of a material selected to have a thermalresistance for optimizing heat transfer from the interior volume intothe medium (fluid). The material's properties considered may include acoefficient of thermal expansion effective to maintain the geometricstructural integrity of the surfaces, effective to be stable in anenvironment comprising the medium, effective to minimize nucleationduring boiling of the medium thereagainst, or a combination thereof.

The inlet may conduct a recycled vapor, generated against the exteriorsurface, into the interior volume, the exterior surface conducting heatfrom the interior volume into a boundary layer formed by the exteriorsurface when contacted by the medium. For example, the material may beselected from the group consisting of metals, polymers, composites, anda combination thereof. One suitable polymer is a fluorocarbon polymer,such as a tetrafluoroethylene (e.g. polytetrafluoroethylene).

The material may selected to be chemically inert and non-reactive withrespect to the medium. It may also be selected to minimize accretion ofcompounds generated in the medium.

A method for improving a process for vapor recompression, may includeselecting a process comprising a plurality of operations combinable assub units to effect the process. Determining a concentration profile ofa material dissolved in a source of the vapor may be done in conjunctionwith determining an influence on the concentration profile. This may bedone by evaluating at least one operation of the plurality of operationshaving a set of operational parameters.

Selecting a target operation from the plurality of operations may bebased on that evaluating. Selecting a control parameter for controllingthe target operation, one may begin manipulating the concentrationprofile by modifying the control parameter. The control parameter may beselected from the group consisting of a mass flow, mechanical work,thermal energy, thermal inertia, a rate of change thereof, and acombination thereof for certain embodiments. In other embodiments alarger group may be considered

Evaluating may consist of evaluating in sequence a pump moving liquidsin the process, a compressor compressing the vapor from the source, anda heater adding heat to the source. It need not include more than thoseactions, but could include evaluating the response time of the source(e.g., thermal inertia).

In one embodiment, evaluating may also be sequentially and in an orderof first, a pump for moving liquids in the process, second, a compressorfor compressing the vapor from the source, and third, a heater foradding heat to the source. These may be evaluated when actually movingliquids, compressing the vapor from the source, and adding heat to thesource.

The method may include analyzing the feed for at least one of theconstituents therein, time variance of the constituents, a source ofsupply, delivery mechanisms, and the like. The method may includemodifying a control corresponding to at least one of a pump, acompressor, a heater, and a combination thereof. It may also includeproviding sensors to detect at least one of a temperature, pressure,flow rate, power, and concentration corresponding to an operation withinthe process. It may beneficially include determining an ambientcondition selected from pressure, temperature, wind, humidity, and acombination thereof.

Evaluating may include determining substantially all (or all) energyinputs into and energy outputs from the process. The method may thusinclude balancing substantially all inputs of energy into and outputs ofenergy from the process. It may add an energy recovery operationproviding energy transfer with respect to at least one of theoperations.

In certain embodiments, a method of removing a contaminant from acarrier may include selecting a liquid operating as a carrier. Acontaminant found in the carrier may be selected or targeted forremoval, reduction, or concentration. A circuit making up a vaporre-compression cycle may have a first region containing nucleateboiling. Introducing into the circuit the carrier containing thecontaminant, one may establish in the first region a concentrationgradient of the contaminant. Controlling the first region may beaccomplished by manipulation of the concentration gradient. The resultmay include returning a condensate, the carrier containing less thansome pre-determined concentration of the contaminant.

The system and method may also return from the first region a brineconcentrating the contaminant. At least one of the condensate exitingthe cycle and a vapor within the cycle may be substantially devoid ofthe contaminant. One or more of the condensate, vapor, and brine mayserve as a feedstock for a subsequent “unit operation” as that term isunderstood in the chemical engineering art.

The feedstock may provide one or more benefits. It may serve as aprecursor for a chemical reaction in the subsequent unit operation. Itmay be sold as a solid or fluid having independent economic value insome market for such commodities. Likewise, it may be further processedto provide a constituent, derivable from the fluid, and havingindependent value in the marketplace. In some embodiments, the fluid maybe reusable directly for recycling in a source process that provided thecarrier to the circuit initially. The feedstock or output of the circuitmay provide increased operational efficiency for a disposition processdisposing of that output, reduction of environmental impact of thecontaminant; improvement in a compliance process in satisfaction of atleast one of a governmental regulation, industry standard, healthstandard, safety standard, and a contractual requirement, or acombination thereof.

A subsequent unit operation may be or include synthesis of hydrochloricacid, synthesis of another acid, hydrolysis, electrolysis, an ionexchange operation; an osmotic separation process, a vaporizationseparation process, coagulation, other chemical separation process,centrifugation, filtration, sluicing, settling, flocculation, andanother mechanical separation process, microwave separation, anothermicrowave treatment, re-injection into a well, a geologic fracturingoperation, blending with another material, reacting chemically withanother material, or a combination thereof.

The contaminant may also be or include a dissolved solid, suspendedsolid, hydrocarbon, salt, heavy metal, other metal, volatile organiccompound, other organic compound, oxide of nitrogen, other nitrogenouscompound, alcohol, oxide of sulfur, other sulfurous compound, calciumcompound, halide, other ion, acid, base, or some combination thereof.

The circuit may include modules for effecting the circuit. For example,a specification defining a system may call out a plurality of themodules, each module implementing an instance of the circuit and itsunit operations. One may size the system to match a source of thecontaminant and provide the plurality of modules, operating together asthe system, and in numbers selected based on an output to be treatedfrom the source.

Methods may include providing a requirement, pre-determined andcorresponding to a source of the contaminant, defining a system having aplurality of the modules, each module having a type and implementing atleast one function specified by the requirement, and then selecting avalue, a number of modules of each type to be included in the system asselected components. The system may then be configured by connecting theselected components.

The method of claim 6, wherein each module of the modules is mounted ona connecting structure and sized to be commercially transportable inaccordance with transportation limitations provided by regulation. Itmay include assembling a facility in a pre-determined configuration byconnecting the connecting structures to one another and rendering themodules interoperable.

A method of separating out a material contained in a liquid may includeproviding, from a source, a liquid operating as a carrier containing amaterial targeted for separation from the liquid. It may provide acircuit constituting a vapor re-compression cycle having a first regioncontaining nucleate boiling and a second region containing vaporcondensation. By introducing into the circuit the liquid, the method mayestablish in the first region a concentration gradient of the materialin the liquid. Controlling the nucleate boiling may be done bymanipulation of the concentration gradient.

Methods may include returning from the second region a condensatecomprising the liquid containing less than a pre-determinedconcentration of the contaminant, and may returning from the firstregion a brine. At least one of a condensate, a portion of the vapor,and a brine, may contain the material, and another thereof besubstantially devoid of the material. Providing a feedstock may beconstituted by at least one of a condensate separated from the material,a vapor separated from the material, a brine into which the material hasbeen concentrated, and a solid comprising the material. A the outputsmay be used as a feedstock sent to a subsequent unit operation.

A system in accordance with the invention may include a circuit forprocessing fluids by vapor re-compression, the circuit comprising anevaporation region. A working fluid may circulate through the circuit. Amaterial contained within the working fluid may be targeted forseparation therefrom. An evaporator, controllable by an operator, may belocated within the evaporation region, and provide control of nucleateboiling by establishing and manipulating a concentration gradient of thematerial in the evaporation region.

The system may be made up of modules constituting the circuit, whereineach module is mounted on a connecting structure and sized to becommercially transportable in accordance with transportation limitationsprovided by regulation. Modules may be connectable (and ultimatelyconnected) and interoperable in a pre-determined configuration when theconnecting structures are secured to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and features of the present inventionwill become more fully apparent from the following description andappended claims, taken in conjunction with the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are, therefore, not to be considered limiting of itsscope, the invention will be described with additional specificity anddetail through use of the accompanying drawings in which:

FIG. 1 is a schematic block diagram of a controlled-gradient,vapor-recompression system in accordance with the invention;

FIG. 2A is a schematic block diagram of the system of FIG. 1implementing sensors and a controller for operation of key apparatus andparameters;

FIG. 2B is a schematic block diagram of the control system, illustratingthe inner-most and outer-most levels of control;

FIG. 2C is a schematic diagram of a mechanism for detecting liquid levelin a tank in accordance with the invention, without interference fromturbulent surface activity;

FIG. 3 is a schematic diagram of various embodiments of optionconfigurations of components for the system of FIGS. 1-2;

FIG. 4 is a schematic diagram of a core within a tank in accordance withthe apparatus and method of FIG. 1, illustrating the activity of theheat and brine convection processes;

FIG. 5 is a chart illustrating the relationship between total dissolvedsolids in a tank of the system of FIG. 1, between the liquid level andthe outlet level of the tank;

FIG. 6 is a chart of curves illustrating the normalized total dissolvedsolids increase in the concentration gradient or density gradient of thetank of FIG. 5, in a system of FIG. 1;

FIG. 7A is a chart of the temperature as a function of height in thetank of FIG. 5, equipped with a core of FIG. 4 in the system of FIG. 1;

FIG. 7B is a description of Raoult's Law governing saturationtemperature in impure liquids, such as production brine;

FIG. 7C is a description of the Clausius-Clapeyron equation describingthe change of temperature in a vapor across a compressor increasing thepressure on that vapor;

FIG. 7D is a description of Dalton's Law of partial pressures in avessel containing multiple gasses;

FIG. 7E is a description of Henry's Law governing the concentration ofabsorbed non-condensable gasses as a function of pressure contributionof those gasses above a liquid in equilibrium;

FIG. 8 is a perspective view of one embodiment of an apparatus inaccordance with FIGS. 1-7;

FIG. 9 is a table representing input variables into an experiment inwhich brine is concentrated from an initial feed water concentrationlevel to an output brine concentration level in an apparatus and methodin accordance with the invention;

FIG. 10 is a chart illustrating curves representing the concentration ordensity gradient change in the experiments outlined by FIG. 9 andimplemented in the system of FIG. 8, showing the normalized totaldissolved solids increase as a function of liquid level in the tank ofthe system of FIGS. 1-9;

FIG. 11 a chart showing the temperature of saturation in the experimentof FIGS. 9-10, and compared with the expected performance of aconventional, completely mixed heat exchange system; and

FIG. 12 is a schematic block diagram of a method of controlling thesystem of FIGS. 1-11, in accordance with the levels of controlillustrated in FIGS. 2A-2B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the drawingsherein, could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the system and method of the present invention, asrepresented in the drawings, is not intended to limit the scope of theinvention, but is merely representative of various embodiments of theinvention. The illustrated embodiments of the invention will be bestunderstood by reference to the drawings, wherein like parts aredesignated by like numerals throughout.

As used herein, terms are to be understood and interpreted broadly.However, alternative, specific terms may be used by way of example, butare to be interpreted as meaning the broader terms. For example asolvent or liquid is exemplified by water, but may be interpreted as anysolvent, liquid, material, medium, carrier, or the like. Similarly, manymaterials may be dissolved as solutes in such a carrier. Solutes may becalled contaminants herein; contaminant simply refers to something to beseparated out, even a desirable material as in distillation. A solventor liquid may be thought of as any fluid to be treated by a separationprocess in accordance with the invention.

Solutes may be liquids, solids, ions, synthetic, natural, mineral,animal, vegetable, or other materials dissolved in the solvent orcarrier. Thus, the term TDS is an example standing for a solutegenerally, dissolved in the carrier as its solvent. Solutes and solventsmay arise in food processing, industrial process fluids or wastewater,alcohol distilleries, sugar processing, petroleum drilling or productionfluids, potable water processing, mining effluent or tailingsprocessing, nuclear coolant or waste liquids processing, runoff or othercollection pond handling, or the like. Brine stands for any solution ofsolute in a solvent, even though it is an example term commonly appliedto dissolved solids and ions in water.

Core materials may be any suitable materials ranging through metals,alloys, stainless, polymers, elastomers, other materials, composites, orcombinations thereof. The core may have bellows structures to changespacing between panels, or other variations supporting positioning,pivoting, tilting (e.g., attitude of roll, pitch, or yaw around anyaxis), sliding, or otherwise optimizing configurations of core panels bypositioning. Such may be useful in processes such as vaporrecompression, evaporator distillation systems, multiple-effectevaporators, and other processing systems, even though otherwisedifficult in some industrial situations.

The core described herein is not a ‘radiator’ like an automobile uses,for several reasons. For example, air through such a radiator is a flowcompletely unrelated to the cooled liquid contained. In contrast, vaporrecompression passes a vapor phase boiled off a liquid phase, through acompressor and back to condense against the outside of the very wallcontaining the boiling.

Quiescent is comparative between flows, and does not mean a completelack of flow or motion, but rather a much slower motion than the flowcompared with it and conventional flows for the function. Nucleateboiling is not limited to boiling initiated at surface nucleationpoints, but boiling due to exceeding the vapor pressure. Confinedboiling is a term of art in the art of heat transfer and is used in itsordinary meaning therein. It is also understood to mean nucleate boilingin a space confined in at least one dimension.

Likewise, fluids include all gases, vapors, liquids, and liquidousflows. Systems or devices in thermal or fluid communication mean thesystems are capable of exchanging heat or fluid, respectively.Containment for fluids may include anything natural or artificial, fromponds, lakes, rivers, and other estuaries to lined ponds, tanks,containers, pipes, conduits, or the like.

By gradient is meant a profile (a variation in one variable, liketemperature or concentration, with respect to another, like space ortime). It need not be linear, nor monotonic (changing always in a singledirection). The profiles often tend in one direction, with localizedvariation due to the dynamics of the system. Typically, a profilechanges more dramatically in an active region (region where heattransport, mass transport, or both are actively occurring between flows,and not just flowing through some containment from one location toanother). A dynamic gradient or dynamic profile is a profile establishedby operation of the invention, and subject to localized variations,variations with time or conditions, or a combination thereof.

Referring to FIG. 1, while referring generally to FIGS. 1-12, a system10 in accordance with the invention may be set in a permanentinstallation, or may be containerized. The basic elements of system 10may include a tank 30.

In the illustrated embodiment, the tank 30 contains a brine 23 that hasestablished therein a gradient of concentration of the dissolved solids.The tank 30 is fed originally by a feed tank 32 through lines 33. Ingeneral, herein, any reference to an item by reference numeral includesa generalized inclusion of such items bearing such a number. A trailingletter after a reference numeral indicates a specific instance of theitem designated by the reference numeral. Thus, the system 10 includes aplurality of lines 33, including, for example, lines 33 a, 33 b, 33 c,and so forth.

The feed tank 32 provides through lines 33 to a separator 34 a flow 35.The flow 35 is typically pre-treated in the separator 34. In oneembodiment, the separator 34 may be configured as a pre-treatment systemfor removal of volatile materials, for example.

In one embodiment of a method in accordance with the invention, thesystem 10 may be used by introducing a brine 23 in an unconcentratedstate into the feed tank 32. This may come directly from a well head, ormay be hauled to a particular location from various petroleum productionfacilities. In the illustrated embodiment, the feed tank 32 may thentransport the brine through a line 33 to a pre-treatment system 34,which typically will operate as volatiles separator 34. Other processesof pre-treatment systems 34 may include adding various chemicals inorder to reduce fouling, scale, corrosion, and the like.

For example, brine received in a feed tank 32 may include numerousmaterials. Dispersed oil products are typically volatiles that vaporizeupon heating. These may include fractions of crude oil that range fromC6 to waxes, tar, paraffin, as well as paraffin soluble organiccompounds. Gasoline and diesel ranges of organic hydrocarbons may beincluded in small amounts. Likewise, various aromatics, such aspolycyclic aromatic compounds may be included. BTEX compounds are notuncommon. Likewise, methanol, phenols, and methane may similarly beincluded.

Not only those organic hydrocarbons but likewise sulfur in variousforms, including hydrogen sulfide (H₂S) may be included. These may beparticularly problematic since sulfates are likely to permanently scaleout on solid surfaces. In order to reduce the scaling by sulfates, scaleinhibitors must be introduced into the brine 23 to maintain a clean feedtank 30. These are not necessarily required, but are highly recommendedfor brines 23 that contain compounds of sulfur.

Similarly, silica, clay, and other inorganic materials may be includedin large or small amounts, dissolved, or undissolved. Typically, silicaand clay are undissolved, and may form particulates. Likewise, varioussalts. Salts may include cations ranging through magnesium, calcium,sodium, and potassium. The anions, which may correspond to theaforementioned cations may include chlorides, sulfates, carbonates,nitrates, and the like. Typically, nitrates are not present in largeconcentrations. Nevertheless, carbonates are typically received inbrines 23 in comparatively large or larger quantities.

Treatment chemicals added in the pre-treatment system 34 may include,for example, ammonium, various compounds of nitrogen, gels, foamgenerating materials, and the like. Similarly, additional ions mayinclude strontium, mercury, lead, chromium, selenium, iron, barium, andso forth. Various naturally occurring radioactive materials such asuranium, radium, and the like may be included. Boron is not all thatuncommon.

In some embodiments, various types of separators 34 may be placed toremove other entrained materials, whether solid, gas, liquid, or thelike. Such pre-treatment systems 34 are numerous and ubiquitous in thescience of pre-treating production brines.

For example, Sears, in U.S. Pat. No. 5,968,321, issued Oct. 19, 1999 andentitled Vapor Compression Distillation System and Method, which isincorporated herein by reference, discloses a distillation system thatincludes a pre-treatment process and apparatus. Similarly, Kresnyak, etal., in U.S. Pat. No. 6,355,145 B1 issued Mar. 12, 2002 and entitledDistillation Process with Reduced Fouling, which is incorporated hereinby reference, likewise discusses various processes for pre-treatment.

From the pre-treatment system 34 or separator 34, the flow 35 firstpasses through a heat exchanger 36, referred to as a brine heatexchanger. The function of the brine heat exchanger is to remove heatfrom brine 23 leaving the tank 30, and to recover that heat into theflow 35 passing into the tank 30.

Ultimately, the concentrated brine from which heat is extracted by thebrine heat exchanger 36 is disposed of in a brine tank 38. The brinetank 38 may be emptied by hauling the brine away, passing the brine intoan evaporation pond, further processing the brine for minerals, heatingor otherwise drying the brine, or other disposition method.

In the illustrated embodiment, a distillate handling system 40 operatesopposite the brine heat exchanger 36 and brine tank 38. That is, forexample, the distillate handling system receives the distilled water asan output from the system 10, and specifically from the tank 30 where ithas been boiled off. The distillate handling system 40 may include avapor trap 41. The vapor trap 41 may be simple or complex and typicallyoperates like a liquid trap (e.g., P trap) in which a column of liquidis contained within a line 33 that traverses both down and back up inorder to maintain a liquid column that cannot be overcome by thepressure of incoming vapor.

The distillate tank 42 operates to collect all the distillate that hasbeen condensed from the closed channels 24 of the core 20. However, as apractical matter, particularly in consideration of control issues, adistillate reservoir 43 may first receive the distillate from the vaportrap 41. Accordingly, the distillate reservoir 43 may be used fortesting the level or rate of generation of distillate.

Following collection in the distillate reservoir 43, the distillate maynext pass to a heat exchanger 44 configured to extract heat from thedistillate, and pass that heat into the feed input line 33 a feedinginto the tank 30. In the illustrated embodiment, the distillate heatexchanger may operate at a fixed rate of flow in both directions.

For example, the brine feeding from the feed tank 32 may be dividedbetween feeds F1, passing through the distillate heat exchanger 44, andF2, passing through the brine heat exchanger 36. Thus, F1 receives heatfrom the distillate, preheating as close as reasonable to thetemperature of the brine 23 in the tank 30. Likewise, feed passing fromthe feed tank 32 through the brine heat exchanger 36 extracts heat frombrine exiting at maximum concentration from the tank, toward the brinetank 38. This preheating of F1 and F2 elevates feed temperatures andrecovers heat that would otherwise be discharged in the distillate tank42 and the Brine Tank 38, respectively.

In the illustrated embodiment, the distillate handling system 40includes a level control 45. The level control 45 operates by sensingthe level of distillate in the reservoir 43. According to the output ofthe level control 45, the system 10 may be adjusted in certain operatingparameters in order to maintain a constant flow of distillate.

In the embodiment of the illustration, it is contemplated that thedistillate outflow to the distillate tank 42 from the distillatehandling system 40 through the distillate heat recovery system 47, willbe operated at a fixed rate. One benefit of an apparatus and method inaccordance with the invention is that the output rate of distillate maybe fixed. Likewise, the incoming brine mass flow rate may be fixed inthe flow 35, divided between the flows F1, F2, regardless of the brineconcentration incoming from the feed tank 32, and regardless of thebrine concentration level discharged into the brine tank 38.

Various embodiments of level controls 45 may be implemented. Forexample, FIG. 2C hereinafter describes one level control mechanismsuitable for operating between a vapor compartment and a liquidcompartment or a vapor region and a liquid region within a tank, whilestill providing accurate, repeatable, reliable readings, without theneed for vents and other condensate removal systems from the vapor sideof the gauge.

The energy sources for evaporation of the brine 23 in the tank 30 comesfrom multiple sources. As a practical matter, an auxiliary heat source46 provides heat to supply the brine 23 in order to elevate thetemperature within the tank 30 to the proper level. Meanwhile, the brineheat exchanger 36 and distillate heat exchanger 44 recover heat fromexit streams in order to elevate the temperatures of F2 and F1,respectively, entering the tank 30.

Thus, the distillate heat recovery system 47 is a source of heatrecovered into the line 33 a, as the brine heat recovery system 80 is asource of recovered heat into the flow 35 c in the line 33 a. Other heatrecovery systems such as engine exhaust recovery may also be employed.Actual sources of heat will typically include only a heater 70 providingheat from an auxiliary source 46, which operates merely to overcomelosses in the system.

The tank 30, may include a level control 48, which may be similar, orcompletely different from the level control 45 on the distillatereservoir 43. Each of these level controls 45, 48 may operatesubstantially independent of the rest of the system 10. However, incertain embodiments, the level controls 45, 48 may operate directly tocontrol the feed 35 a through the lines 33 a, in order to match massflow rates according to conservation of mass.

An ancillary option at an appropriate place in the system 10 may be adistillation column 49. It has been found useful in some productionwater sources to implement a distillation column 49 in order to removeheavier materials, such as distilled water, in a stripping section,while separating out lighter components, such as methanol or the like,in a rectifying section at the top thereof. Thus, the distillationcolumn 49 is an optional element that may or may not be includeddepending upon the particular site being serviced by a system 10.

A compressor 50 compresses vapor 27 originating in the tank 30 in thebrine 23, and collecting above the brine 23. The compressor 50 isresponsible to raise the pressure in the vapor 27 according to theClausius-Clapeyron equation relating temperature rise to pressure rise.Accordingly, the vapor 27 passes through the compressor 50 and is fedback into the manifold 19 of the core 20.

The pressure downstream of the compressor 50 exists substantially thesame in the conduit 18, manifold 19 a, and the close channel 24. Thedifferential in pressure between the upstream side of the compressor 50and the downstream side thereof effects a pressure of saturationcorresponding to a higher temperature of saturation.

Heat is transferred due to the temperature differential between theclosed channels 24, of compressed vapor, and the open channels 22, inthe brine 23. Heat from the condensing, saturated vapor 27 in the closedchannel 24, transfers into the brine 23.

In some embodiments, a vapor handling system 52 may be mounted near orat the top of the tank 30. In the illustrated embodiment, the vaporhandling system 52 may include, for example, a mist eliminator 54.Typically, a mist eliminator 54 is responsible to remove droplets ofwater, which may entrain droplets of brine 23, from the vapor 27 andbring with them the risk of carrying dissolved solids toward thecompressor 50.

Various embodiments of vapor handling systems 52 may be considered. Inaddition to the mist eliminator 54, for example, a deaerator 56 may beincluded as part of the vapor handling system 52. De-aerators at thisstage need not be excessively large, nor vent substantial quantities ofthe vapor 27.

For example, in one apparatus and method constructed for experiments,and producing approximately 100 barrels per day of distillate in thedistillate tank 42, a de-aerator 56 was sized by conventional chemicalengineering principles. Henry's Law, which relates concentrations ofnon-condensables or other vapors within liquids, according to thepartial pressure and a physical constant, as described hereinbelow,required a reservoir of about twenty liters. Accordingly, the deaerator56 needed only about five liters to be vented approximately once per dayduring operation.

In general, a plenum 58 above the brine 23 in the tank 30 may be sizedto provide a dwell time or accumulation time for vapors 27 in order toenhance mist elimination.

Numerous manufactures produce compressors of constant displacement,positive displacement, and so forth. For example, Ingersoll Rand,Dresser, and other companies produce compressors 50 suitable forapplication in a system 10 in accordance with the invention. Likewise, aplenum 58 may be sized according to the rating of a compressor 50.

Ultimately, the brine 23 is concentrated by boiling and vaporizing thebrine 23 into vapor 27. As vapor 27 leaves the brine 23 as bubbles, andenters the plenum 58, the residual dissolved solids within the brine 23increase in the region about the vaporized bubble. This increase indissolved solids in this surrounding brine 23 results in higher densityand a net downward flow of this more dense brine 23.

Ultimately, the tank 30 establishes a concentration profile or gradient,in which the brine 23 of lowest concentration exists at the interfacebetween the brine 23 and the vapor 27. Accordingly, the heaviest or themost concentrated brine 23 is established at the output level of thetank 30. The function of the system 10 is to concentrate brine 23 fromwhatever concentration exists in the feed tank 32 to a much greaterconcentration.

As the brine 23 loses water into vapor 27 collected in the plenum 58,localized concentrating processes occur around every bubble formed.These localized concentrations, result in localized descent of heavierbrine 23 relative to lighter brine.

For example, the brine 23 in the feed tank 32 has less dissolved solids,and is lighter, per cubic inch or cubic centimeter than the brine in thebrine tank 38. In the locality of bubbles, a density differentialdevelops beside a bubble that has vaporized. The bubble leaves behindits share of dissolved solids to be absorbed by neighboring liquid watermolecules in the brine 23. Ultimately, with the continuing process ofheating and evaporation occurring within the open channels 22 as aresult of the heat transferred from the closed channels 24, a continuingconcentrating process occurs within each open channel 22.

As a direct result, heavier, more concentrated brine 23 moves downwardseeking density equilibrium among equally agitated boiling or nearboiling neighbors. Thus, in steady state the maximum concentration ofdissolved solids exists at the outlet of the tank 30 and the minimumdensity and minimum concentration of dissolved solids exists at theinterface between the brine 23 and plenum 27. This has been demonstratedin experiments.

A concentrate handling system 60 is responsible for handling theconcentrated brine 23 exiting the tank 30. In the illustratedembodiment, the concentrate handling system 60 includes a slurryhandling system 62. The slurry handling system 62 is responsible forhandling such items as high density precipitates that may form sludge,or other suspended solids at high concentrations in liquid. Accordingly,such materials may be separated from the brine 23 of the tank 30 anddirected to disposition different from the brine in the brine tank 38.

Similarly, a reservoir 64 may act as a settling tank 64, as well asconcentrator 64. As a practical matter, concentrations, having orcausing the greatest stratification, occur in regions whereconcentrating activity, such as boiling evaporation are found. In theillustrated embodiment, that region is the region within the openchannels 22. In contrast, the reservoir 64, lacking any heating orevaporation mechanism concentrate may operate as a settling region, andtypically does not concentrate substantially further.

Likewise, the brine concentration system 60 may include a variety ofmechanisms within the slurry handling system 62 to assist in removingprecipitates and other solids from the walls, floors, and the like ofvarious components.

Solids removal equipment is known in the art and may include vibrationsystems, scraping systems, augers, combinations thereof, and the like.Ultimately, a slurry holding system 66 may actually be separated byvalving from the slurry handling system 62, and only receive brief andperiodic discharges of solidus flows into the slurry holding system 66.Such systems may be manual, automatic.

Following passage through the pre-treatment system 34, the brine 23 maypass through a flow divider 74, such as a valve or system of valvesdividing the overall flow in the lines 33 from the feed tank 32 into F1and F2, illustrated by feed 35 a passing through line 33 a. The flowdivider 74 is responsible for maintaining a constant flow to thedistillate heat recovery system 47, and a variable flow to the brineheat exchanger 36. The control of the relative proportion of these flowswill be discussed hereinbelow.

In the illustrated embodiment, the flow 35 a through the lines 33 arepresents two flows. A fixed rate through the distillate heat exchanger44 is matched to the fixed flow of the distillate through the distillateheat exchanger 44.

In contrast, the fresh brine from the feed tank 32 passing through thebrine heat exchanger 36 is adjustable, commensurate with the flow ofbrine concentrate out of the tank 30, through the line 33 c into thebrine heat exchanger 36. In all cases, metered pumps, controlledtypically by being fixed displacement pumps 76, may be placed in thelines 33 to control the rates of the flows 35 into and out of the tank30. For example, feed pump 76 a may control the flow of brine from thefeed tank 32 through the distillate heat exchanger 44.

Likewise the pump 76 b controls F2, or the flow 35 a passing from thebrine heat exchanger 36 into the diffuser 68 in the tank 30. Similarly,a brine pump 76 d may control the feed of the concentrated brine fromthe tank 30 through the brine heat exchanger 36. A pump 76 c may controlthe flow of distillate into the distillate heat exchanger 44, and may bematched by mass flow of the brine pump 76 a.

Continuing to refer to FIG. 1, while referring generally to FIGS. 1-12,a system 10 in accordance with the invention typically feeds preheatedbrine 23 through the lines 33 a into a diffuser 68. The diffuser 68 isdescribed in various options in FIG. 3. By whichever mechanism isselected, the diffuser 68 has the effect of distributing the brine 33 a,in a fashion that will allow the brine 23 from the lines 33 a todistribute across the maximum extent of the core 20.

For example, the cross-sectional area or foot print of the core 20 inthe tank 30 represents a particular area of interest. That area presentsthe bottom openings of all the open channels 22. Accordingly, a diffuser68 may be responsible to distribute the flows 35 a of the lines 33 awithin the core 20. If all the flow 35 a passes into a single openchannel 22, the efficiency of the core 27 will be different from thatachieved if all open channels 22 of core 20 have a reasonably equalopportunity to receive a portion of the flow 35 a.

An auxiliary heater 70 is responsible to add heat received from a heatsource 46 or an auxiliary heat source 46. In the illustrated embodiment,the auxiliary heater 70 is positioned below the bottom of the core 20.

In certain embodiments, the auxiliary heater 70 may be placed on a wall31 of the tank, rather than inside the tank 30. Likewise, the auxiliaryheater 70 may be respectively positioned with respect to the diffuser68, such that auxiliary heat source 46 feeds heat directly intoconcentrated brine at the bottom of the tank 70, rather than into theincoming brine 35 a flowing into the diffuser 68.

In some embodiments, a diffuser 68 may not be required. In others, anengineering selection may be made between heating the incoming brine 35a with the auxiliary heater 70, and allowing the incoming brine flow 35a to simply rise due to saline convection (TDS content convection) tothe top of the core 20 without the benefit of carrying any heat.

In FIG. 1, diffuser 68 is positioned at a level below the auxiliaryheater 70. Thus, the flow 35 a from the input lines 33 a emitting fromthe diffuser pass through the layer of heated brine created by theauxiliary heater 70. This provides a heat transfer mechanism for heatingthe tank brine 23. In some embodiments, the auxiliary heater mayactually be located in the diffuser. In other embodiments, the auxiliaryheater 70 may be attached to the inside or outside of a wall 31 of thetank 30. In other embodiments, the auxiliary heater 70 may actually bein the lines 33 a feeding into the tank 30.

In order to monitor, and subsequently control operation of, the system10, sensors 72 may be installed in the system 10. Sensors 72 may includesensors 72 to monitor pressure, temperature, concentration of dissolvedsolids, combinations thereof, or the like. In the system 10,concentration effectively improve heat transfer, and mass transfer(evaporation and condensation, for example) by virtue of even smalldifferences in concentration. Hence, temperature, pressure, andconcentration measures are significant as control parameters in thebrine 23 and the vapor 27. Control of system 10 may require amultiplicity of these sensors 72.

Nevertheless, with such items as the compressor 50, lines 33, conduits18, and other fixtures, pressures may vary throughout the system 10.Meanwhile, inasmuch as the system 10 operates about saturation pressuresand temperatures, temperature is an indicator of pressure, and viceversa. Thus, each may be sensed, and steps may be taken to assert activecontrol in accordance with established functional relationships.

Concentration profiles, which may be referred to as gradients, ofdissolved solids are established within the brine 23 of the tank 30, andthus localized density may be implied by those concentrations.Accordingly, density changes, altitude changes, together with anypressure changes within the plenum 58, may add up to provide acomparatively wider variety of pressure and saturation temperaturevariations at points throughout the tank 30 than would a mixed tank 30.Thus, monitors and control systems may be in place to read the sensors72 and feed that data to actuation devices.

In the illustrated embodiment, sensors 72 a are positioned within theopen channel 22 exposed to the free stream or bulk of the tank 30.Sensors 72 b are located within the closed channel 27. Sensors 72 cdetect conditions within the tank 30 near the wall 31. The sensors 72 cmay be placed at the wall, but will more typically be placed in thebrine 23 spaced from the wall 31, but mounted to the wall 31. Sensors 72d exist in the plenum 58 to detect conditions therein.

Likewise, sensors 72 e in the vapor handling system 52 detect conditionstherein, while sensors 72 f monitor the heaviest brine 23 concentratedat the bottom of the tank 30. The region hosting the sensors 72 f doesnot have any portion of the core 20 active therein but may be importantin the control of system 10.

The compressor 50 may be monitored by sensors 72 g on the upstream orinlet side thereof, and sensors 72 h on the downstream or outlet sidethereof. Ambient conditions may be monitored by sensors 72 j external tothe tank 30, located in the environment to sense ambient and atmosphericconditions.

From the plenum 58, the conduits 18 carry the vapor 27 into thecompressor 50, and from the compressor 50 into the plenum 19 a of theclosed panels 24 or closed channels 24. The vapor 27 within the closedchannel 24 eventually condenses to form the condensate 25 in the bottomof the closed channel 24. Eventually, the lower plenum 19 b of theclosed channels 24 may be completely filled with liquid.

Nevertheless, it may be possible that some vapor 27 may be circulatedthrough the distillate 25 or the condensate 25 at the bottom of theclosed channels 24. Accordingly, the flow from the closed channel 24into the vapor trap 41 may contain both gas and liquid phases of thecondensate 25.

Meanwhile, the level control 45 monitors the level of condensate 25 inthe reservoir 43. Ultimately, the reservoir 43, controlled by the pump76 c passes the distillate through the distillate heat exchanger 44 andon to the distillate tank 42.

Referring to FIG. 2A, while continuing to refer generally to FIGS. 1-12,the system 10 may include a controller 84. In general, controller 84includes at least one processor, and typically the complete inputsystems, output systems, processing facility, memory, and so forth of acomputer. The controller 84 may receive data, process data, store data,and so forth. The controller 84 is responsible to receive inputs fromsensors 72 throughout the system 10.

Specifically, the controller 84 will receive information in the form ofdata regarding temperatures, pressures, concentrations, and so forth aswell as flow rates, and the like from the various components describedhereinabove with respect to the system 10. In the illustratedembodiment, the controller 84, although illustrated multiple times, maybe a single processor-based system, or multiple processors. Thecontroller 84 may be consolidated, distributed, or any otherconfiguration. The controller 84 may be a single controller, multiplecontrollers, or a system 84 of controller.

Meanwhile, the controller 84 is also responsible to send command singlesback to the various pumps 76, and to the auxiliary heat source 46, theauxiliary heater 70, or both. Controller 84 may control the input ofheat from the auxiliary heat source 46, as well as the input of power tothe compressor 50.

In general, the controller 84 commands 86 or sends outputs 86 ascommands 86 to the various devices and components within the system 10,and receives inputs 88 or reads 88 the inputs 88 from those and othercomponents. In the illustrated embodiment, the controller receivesinputs likewise from such components as the level control 48, and thelevel control 45.

However, typically, the level controls 45, 48 operate within themselvesto control the level directly, in a manner well understood in the art.

Referring to FIG. 2 b, a control schema 90 identifies four levels ofcontrol. At level zero 92, the control system 90 or control schema 90operates to control the liquid mass. Thus, the zero level 92 may also bereferred to as the liquid mass control 92. Likewise, the first level ofcontrol, above zero, is the vapor mass control 94. The liquid masscontrol could operate completely independent of any other control systembut is incorporated as the basic or zero level of control in schema 90.

Likewise, the first level 94 or the vapor mass control level 94 dealswith the vapor 27 in the plenum 58, through the compressor 50, and intothe closed channels 24 of the core 20. These depend on a formularelating the work done by the compressor 50 to the pressure andtemperature within the vapor 27 passing through the compressor 50. Thus,while the level zero system need only track and control a value of aliquid level, the vapor mass control 94 has a more sophisticatedresponsibility. It must track the liquid levels in the liquid levelcontrollers 45, 48, and also operate the compressor 50 in responsethereto in order to assert control over the principle energy input tosystem 10, the worth of the compressor 50.

The second level control 96 or the energy control 96 is responsible forcontrolling a rate of change of energy inputs into the system, such asheat into the auxiliary heater 70. Accordingly, the energy control 96must operate on the basis of a formula, algorithm, computer program,from the conditions of temperature, pressure, concentration, and thelike within the tank 30 and other components of the system 10, andassert control over the regulation of heat through the heater 70 as partof controlling the energy of system 10.

Significant in operation of the energy control is the fact that the timeof response of the tank 30 is measured in hours, sometimes many hours.By contrast, the pressures reported by the sensors 72 g, 72 h in theplenum may facilitate a compressor response in seconds. Thus, thecompressor 50 may be adjusted in current draw, and thus speed orvelocity. Therefore, volumetric flow rate can be adjusted almostinstantaneously. By contrast, the addition of energy by the energycontrol system 96 will not be evident for a much longer period of time.

In contrast, a liquid level may be observed by sight in a manometer orgauge. However, energy flows cannot be observed physically, typically,and the rates of change and the relationships within the system 10 arenot obvious, nor intuitive.

The third level 98 of control or the system predictive control 98 isstrictly algorithmic and computational in its implementation. Thesophistication required is high. Many parameters, many sensors,thermodynamic considerations, material properties, and the like all gointo an algorithmic determination by the system predictive control 98 ofwhere system 10 is operating and where it should be.

For example, the system predictive control system 98 is responsible toreview all data in the controller 84, from all sources, including thehistory of operation of the system 10. The system predictive control 98may interpolate, extrapolate, or use other numerical method solutions tosolve complex equations involving partial differentials of any value,rate of change, or the rate of change of the rate of change ofvariables, in order to precisely and adequately predict control setpoints. It may control assert control over the heater 70, the compressor50, level controls 45, 48, pumps, and other volumetric flows.

The system 10 is sufficiently robust, even resilient, that it canaccommodate wide variations in inputs. For example, brine concentrationrates of from approximately 10,000 parts per million of total dissolvedsolids up to greater than 150,000 parts per million of total dissolvedsolids may be provided as inputs into the system 10. Likewise,substantially any output concentration, from such values to above200,000 parts per million may be accommodated.

This predictive control system 98 may provide a substantial advantage tothe system 10 by calculating the optimum set points for controlparameters sent by way of commands 86 to the components. The system 10may thus obtain optimum energy efficiency, brine 23 throughput todistillate 25, and so forth.

Referring to FIG. 2 c, a common problem in boiling regimes such as thevapor-liquid interface 100 of tank 30 between brine 23 and vapor 27 isthe variable nature of the fluid level. The configuration of a meter 93overcomes this problem. This may be important for the control schema 90.

In one embodiment of a system 10, the plenum 58 may provide a pressuresource to a meter 93. The meter 93 may detect a pressure differential,and thereby provide processing by the controller 84 or by imbeddedprocessing, the liquid level 100 in the tank 30. Similarly, such a meter93 may be embedded or attached as a liquid level control 45 or 48.

In the illustrated embodiment, a line 95 from the vapor region, in thisinstance the plenum 58, will fill with vapor 27, which will condense andfill the line 95. Meanwhile, the brine 23 within the tank 30 may feedthrough the line 97. The two lines 95, 97 thus feed opposite sides of agauge 93 such as manometer, of any configuration. This may be amanometer, gauge, meter, or the like. Likewise, the line 97 may serve asa common reference to other gauges 93 elsewhere in the system.

Referring to FIG. 3, in one embodiment of an apparatus 10 in accordancewith the invention, a tank 30 may receive input flows 35 a into adiffuser 68. Those input flows 35 a are received from the feed tank 32,and may pass through a pre-treatment system 34. In one presentlypreferred embodiment, the brine flow 35 a passing through the brine heatexchanger 36 receives heat from the brine 23 exiting the tank 30 throughthe line 33 c, as controlled and driven by the pump 76 d. In such anembodiment, the heat exchanger 36 may be set up in any one of severalalternative configurations.

In one embodiment, the heat exchanger 36 may be configured as a singleheat exchanger in which the flow 35 a of incoming brine is counterflowing contrary to the direction of the exit brine flow 35 c flowing inline 33 c from the bottom of the tank 30. In such a configuration, thedwell time, heat transfer coefficient, available surface area, and thelike may all be fixed, to the extent that the heat exchanger 36 may notbe reconfigured.

However, in most presently contemplated embodiments, the flow rate 35 aand its corresponding flow rate 35 c may be used as control variables.As in FIG. 2B, the control of energy typically includes the control ofheat addition to incoming brine 23 preheated by the heat exchanger 36.Meanwhile, the zero level 94 from FIG. 2B includes the level control.One of those level controllers 48 controls the liquid level 100 of thebrine 23 in the tank 30. Accordingly, the flow 35 a into the tank 30 maybe used, as a control variable.

As explained, the flow rate 35 a through the distillate heat exchanger44 with the corresponding output flow of distillate 25 through thedistillate heat exchanger 44 may be fixed and matched to one another.The mass flow rate for adjusting the level of brine 23 in the tank 30may be that control by the level control 48, altering the flow rate ofthe F2 through the pump 76 b and the heat exchanger 36.

Thus, in conditions wherein the incoming flow 35 a through the brineheat exchanger 36 is comparatively low F2 may reduce to less than onethird of the flow through the distillate heat exchanger 44. In such anembodiment, relatively little heat exchange surface area is required.Thus, reduction to a single heat exchanger 36 may be appropriate.

Circumstances wherein the brine heat exchanger 36 receives a greaterproportion of flow in F2 than the distillate heat exchanger 44 receivesfrom F1, the brine heat exchanger 36 may instead carry two or more timesthe volumetric flow rate of the incoming flow 35 a compared to that ofthe heat exchanger 44 with its controlling pump 76 a.

Thus, it may be advisable to provide longer dwell times, greater surfacearea, or both during conditions when a greater flow rate (comparatively)passes through the brine heat exchanger 36, than the distillate heatexchanger 44. Likewise, as flows change, the number of heat exchangers,the area available, the dwell time, or some combination thereof may bevaried.

Referring again to FIG. 3, multiple heat exchangers 36 may be configuredin either a series or parallel configuration, valving systems may beprovided to engage one, two, three, or more heat exchangers 36 in aparallel configuration. In this way, the number of heat exchangersneeded may be engaged, without subjecting the flow 35 a, or the flow 35c to excessive distance, and therefore additional fluid dynamic drag tobe overcome by the power of the pumps 76 b, 76 d.

In contrast, flows may be slowed, and dwell times increased, while alsoincreasing the available surface area by arranging heat exchanges in aseries configuration. In a series configuration, pressure losses may becomparatively larger. Also, valving cannot be used to direct flowsbetween heat exchangers 36, as all flows pass through all heatexchangers 36.

Depending upon the range of operational parameters to which a system 10may be subjected, a single, multiple, series, or parallel arrangement ofheat exchangers 36 may be configured in the lines 33 a, 33 c in order toaccommodate heat transfer between the flows 35 a, 35 c.

By way of reference, in one embodiment of an apparatus and method inaccordance with the invention a six fold variation in flow rate throughthe brine heat exchanger 36 necessarily changed the flow speed and, theflow profile. As such flows may be partially laminar and partiallyturbulent. As will be appreciated by those skilled in the art, suchvariations affect the net dwell time during which heat transfer can takeplace, the log mean temperature difference existing between the flows 35a, 35 c in the heat exchanger 36, and so forth.

Therefore, the distillate heat exchanger 44 may be designed for the flowrate output for which a system will be operated continuously. Incontrast, the brine heat exchanger 36 must be tasked with the controlprocess responsibility of matching the net flow through the systemaccording to the brine concentration ratio of incoming to outgoing brine23.

Continuing to refer to FIG. 3, specifically, while referring generallyto FIGS. 1-12, a diffuser 68 in an apparatus 10 in accordance with theinvention may be responsible to introduce the flow 35 a into the tank30. It has been found that several configurations may be considered,each with a somewhat different effect.

Inasmuch as the tank 30 establishes a gradient of concentration from thelowest concentration of total dissolved solids at the top of the liquidlevel in the tank 30 to a highest concentration of dissolved solids atthe bottom of the tank 30. Two mechanisms tend to operate to exchangeheat and mass between the incoming flow 35 a and the brine 23 in thetank 30 itself.

By virtue of initial velocity of introduction of the flow 35 a into thetank 30, momentum transfers between the incoming flow 35 a and thesubstantially quiescent brine 23 in the tank 30. Thus, mass may beexchanged between the jet and its consequent plume and the brine 23 inthe tank 30. Momentum transfer occurs as the jet interacts with thesurrounding brine 23, thus mixing, broadening, and increasing theconcentration in the jet, as it mixes with the brine 23 in the tank 30.

Likewise, another mechanism, entirely different therefrom in itsmotivating force and energy, is the brine density plume. A buoyancedifference between the more dense brine 23 in the tank 30 and the lessdense introductory brine flow 35 a from the feed tank 32 results in abuoyant force on the incoming brine flow 35 a. Accordingly, the brineflow 35 a tends to rise as a lighter fluid 35 a within the heavier brine23 of the quiescent tank 30. This rise also results in a velocity upwardby the incoming brine flow 35 a, resulting in a plume with aspects ofthe jet-like behavior. For example, the rising, lighter flow 35 a risesthrough the heavier quiescent brine 23 in the tank 30, mixing therewith,broadening the plume, entraining surrounding brine 23, and resulting inan exchange of momentum as well as content (dissolved solids).

A function of a diffuser 68 is to reduce the effect of a velocity-basedmomentum jet from the incoming velocity of the flow 35 a. Nevertheless,in certain embodiments, the diffuser 68 may simply be replaced by a jet.

In FIG. 3, the line 33 may connect to a diffuser 68 in which the lineand the diffuser 68 are both circular in cross section. For example, thediffuser illustrated in the top embodiment illustrates an expansion ofthe diameter from the diameter of the line 33 as a bell, such as a bellon the trumpet.

Thus, the effective cross sectional area is gradually increased,resulting in a commensurate decrease in the velocity of the flow 35 aintroduced by the diffuser 68. In the illustrated embodiment, the wall31 is penetrated for installation of the diffuser 68. Thus, the diffuser68 introduces the flow 35 a through the wall 31.

In the schematic diagram of FIG. 1, the diffuser 68 is illustrated belowthe core 20. Each potential location has benefits.

The diffuser 68 presents no horizontal surfaces. It provides, in fact,no accessible surfaces on which descending materials from theconcentrated brine 23 of the tank 30 may accumulate.

The middle embodiment of the diffuser 68 illustrated in FIG. 3 isconfigured more in a fan-like shape in which the net area of the line 33is increased in the diffuser 68, but not with a circular cross-section.Here, the thickness and width of the fan-like diffuser 68 may beselected in order to provide a flow velocity for the flow 35 a asdesired.

In one embodiment, such a diffuser 68 may be oriented to discharge theflow 35 a in a vertical direction below the core 20. In anotherembodiment, the rectangular cross-section of the outlet of the diffuser68 may be configured to be a square, and may cover a comparativelylarger fraction of the area under the core. However, in the illustratedembodiment, the diffuser 68 discharges the flow 35 a directly throughthe wall 31, and does not present any of its structure within the tank30 itself.

The lower configuration of a diffuser 68 in FIG. 3 may be constructed inany of several arrangements. The illustrated embodiment shows the line33 ported directly through the wall 31, resulting in a jet flow 35 ainto the tank 30. Of course, any degree of change in the cross-sectionalarea from the line 33 to the output of the diffuser 68 may be selectedand may be appropriate. Just as the other embodiments may be arranged topass the flow 35 a through the wall 31, or upward into the core 20directly, from below the core 20, this embodiment may be arranged in anysuch manner.

In fact, the flow 35 a may be directly horizontally vertically, orobliquely with respect to the bottom of the core 20. In someembodiments, the flow 35 a may be introduced through a plate withapertures, through a plurality of lines 33, through various diffusers68, through a bank of diffusers, or the like. Nevertheless, in theillustrated embodiments of FIG. 3, the diffusers 68 remain outside thewall 31. Here they are able to further reduce the components subject tothe destructive forces of the concentrated brine chemistry. They alsoreduce the tendency toward scaling, fouling, accumulation ofprecipitants, and the like.

Referring to FIG. 4, while continuing to refer generally to FIGS. 1-12,a system 10 in accordance with the invention may include channels 22open to the surrounding tank from a top liquid level 100 in the tank 30,to a lowest outlet level 101. Meanwhile, each panel 102 around eachclosed channel 24 forms a mechanical barrier between the vapor 27 andcondensate 25 within the closed channel 24, and the brine 23 in openchannels 22, which are effectively contents of the tank 30.

Each panel 102 presents an outer surface 104 in contact with the brine23 in the open channel 22. An inner surface 106 of the wall 26 is incontact with the vapor 27 or condensate 25 in the inner or closedchannel 24. Heat is transferred from the high pressure region, having ahigher saturation pressure and higher saturation temperature in theclosed channel 24. As described with respect to FIG. 1, the compressor50 compresses the vapor 27 from the plenum 58 to a higher pressure, andcorresponding temperature in accordance with the Clausius-Clapeyronequation illustrated in FIG. 7C. The lower pressure and temperatureregion is represented by the plenum 58 and the open channels 22 in thetank 30.

Thus, heat transferred from the closed channel 24 passes through thewall 26 subject to the heat transfer coefficients on the inner surface106 and outer surface 104 of the wall 26. Ultimately, convection cellsdue to thermal convention may occur. Thermal convection is the result ofbuoyancy, a density decrease by a fluid that has been heated compared toits surrounding and comparatively cooler neighbors.

For example, to the extent that the tank 30 represents brine 23 that hasbeen stratified, stratification in response to brine density differencesis several times more significant than the buoyance differential due toa temperature difference. Accordingly, hotter brine 23 may still remainlower, or at a lower level, within the tank, due to the fact that itsdissolved solids content prohibits its rising in response to thermalbuoyance effects.

Nevertheless, buoyance differentials due to heat addition, rendering thehotter material to be of lower density, and thus lighter, may result inB{hacek over (e)}nard cells 108 or B{hacek over (e)}nard convectioncells 108. However, these will exist only locally within material havingthe same density with respect to dissolved solids. The cells 108 tend tomove heat from the wall 26 into the bulk of the brine 23 in the openchannel 22.

One advantage of a profile (e.g., brine concentration gradient or adensity variation with depth) due to dissolved solids concentrationsincreases with depth within the tank 30 and the open channels 22 is thefact that rather than rising immediately along the wall 26, heated brine23 may remain localized, thus contributing to increase temperature at acomparatively lower level.

In this way, heat may be transferred continually from the wall 26 intothe brine 23 of the open channel 22, even though the temperaturedifferential between the vapor 27 in the closed channel 24 may be nearerto the temperature of the adjacent brine 23 in the open channel 22. Heattransfer still continues because the convection cells 108 did notnecessarily become general along the entire height 116 of the panel 102.Rather, energy is “pumped” away from wall 104.

Stated another way, brine 23 at a particular level in the open channel22 may still continue to pick up heat, and may cause a generation ofbubbles 100 at the outer surface 104 of the wall 26, which mightotherwise not be able to occur. Compared to the illustrated embodimentand the apparatus in accordance with the invention in free convection,if the tank 30 were full of clean water, heated liquid would always risein the presence of comparatively cooler liquid. Thus, all the hottestliquid would rise to the top.

In contrast, with stratified brine, hot liquid may exist and remain atthe bottom. In fact, a reverse temperature gradient, in which thehottest temperature is at the lower end of the panel 102 is entirelypossible, depending on the heat transfer dynamics of the system 10.

In general, bubbles 110 are generated at the outer surface 104 of thewall 26 of the panel 102 anytime localized brine 23 achieves thesaturation temperature for its localized pressure. Pressure varies withdepth, and density of the brine as well as the overhead pressure withinthe plenum 58. Thus, lower in the open channel 22, one expects andobserves higher pressure.

Moreover, due to the density profile (e.g., gradient) or concentrationprofile (e.g., gradient), saturation pressures and temperatures riseeven further. Nevertheless, inasmuch as the temperature within theclosed channel 24 is higher than the temperature in the open channel 22,heat transfer may still occur across wall 26, and bubbles may begenerated at the lower extremities of the panels 102.

This phenomenon has been observed in practice during experiments. Forexample, in free convection with a condensing vapor 27 within a closedchannel 24, wherein the outer channel 22 or open channel 22 contained nosaline gradient, the formation of bubbles 100 occurred only within thetop 5 percent of the height 116 of the panel. In contrast, bubbleformation was observed within the bottom 20 percent of the open channel22, when the open channel 22 contained stratified brine 23.

As each bubble 100 is formed, it would typically nucleate at a site onthe outer surface 104 of the wall 26 of the panel 102. However, it willquickly separate as it grows, and move from a position illustrated bythe bubble 100 a to a position in the free stream of the open channel 22illustrated by the bubble 100 b.

It has been observed that as bubbles 100 grow, due to heat addition,mass addition, and even due to a simple rise in altitude reflecting areduced surrounding pressure, the bubbles 100 have been observed tostrip the boundary layer from the surface 104 of the panel 102. Thistriggers the generation of clouds of bubbles as illustrated by thebubbles 100 d of FIG. 4. These bubbles 100 d likewise appear to be ableto grow and rise. Nevertheless, they may not necessarily nucleate at thewall 26 but may be generated by an infusion of heat due to thedisruption of the thermal and fluid boundary layer as understood in theart of heat transfer.

As the bubbles 100 continue to rise, they tend to grow in size, and tendto coalesce with one another. They begin to form larger bubbles, andtend to move toward the brine 23 in the open channel 22, and away fromthe wall 26. In fact, as a practical matter as a bubble flow 112 rises,brine is displaced, and a corresponding downward flow 114 of thesurrounding brine occurs. A simple mass or volumetric analysisillustrates that as mass rises in the open channel 22, a certain amountof the mass must go down and take its place. This results in a flow 114around each bubble 100, as illustrated.

As a result of the formation of each bubble 100, vapor 27 leaves thebrine 23. Salt, the chemicals listed hereinabove that may be containedin the brine, and the like, may be volatile and nonvolatile. Suchcontaminants as methanol, may evaporate into the vapor 27. However,salts, dissolved solids, and the like must remain behind and do notevaporate.

Accordingly, the flow 114 around each bubble 100, at the time offormation of the bubble 100, necessarily receives the dissolved solidsthat cannot vaporize. Experiments on apparatus and methods in accordancewith the invention demonstrate a downward flow 114 of heavier brine,resulting in a net gradient having the lowest concentration of dissolvedsolids at the top surface 100 of the liquid, or the liquid level 100 andthe highest concentration of dissolved solids at the bottom of the tank30.

In general, the height 116 of the panel 102 may be selected to optimizeheat transfer. Likewise, the distance or thickness 118 across the wall26 may be selected for structural and thermal considerations. Similarly,the width 120 of the open channels 22 may be selected in order that thebubbles 100 c coalescing together do not obstruct the channel 22, nordry the outer surface 104 of the panel 102. Such drying of the surface104 may result in additional scaling, and has been observed toexacerbate corrosion of the wall 26.

The width 122 or thickness 122 of the closed channel 124 may be selectedto optimize heat transfer and permit flow by natural convection, thuslimiting or eliminating the need of conventional heat exchange, whereinpump energy is used to drive all flows. By contrast, in the illustratedembodiment, the open channel 22 operates by a saline convection ordissolved solids convection with the brine. This is based on buoyancedifferentials between various flows and regions of the brine 23.Similarly, the vapor 27 within the closed channel 24 as it condenses onthe inner surface 106 of the panel 102 eventually forms a condensate 25collecting at the bottom thereof and exiting out the plenum 19 b forliquids.

It has been found that the height 124 or distance 124 between the top ofthe panel 102 and the liquid level 100 may be positive. In someembodiments, it has been found that heat transfer rates may be effectedby vigorous boiling of bubbles 100 c near the top of the panel 102. Ithas been found most effective in the presently contemplated embodiments,as demonstrated by experiments, to maintain the liquid level 100 abovethe top of the panel 102.

The core 20 will typically be spaced a distance 126 from the outletlevel 102 of the tank 30. Typically, a significant volume in the plenum58 above the liquid level 100 tends to provide a volume against whichthe compressor 50 may draw. Similarly, a larger depth 126 between thetank outlet level 101, than herein illustrated schematically is desired.

The height 126 is illustrated by a cut line indicating that anyadditional distance may be added therein. Though not shown in theillustration, such an addition provides the possibility of increasing ofhighest density brines 23 from the open channel 22 toward the bottom ofoutlet level 101 of the tank 30.

Nevertheless, the activity within the tank 30, and specifically when theopen channels 22 is a densification or increase in concentration ofdissolved solids in the brine 23. It has been found generally that theregion, illustrated by the height 116 of activity of the concentratingprocess, is the region that sees the largest change in density profile.Accordingly, the density within the height 126 of the region below thepanels 102 does not show the intensity of the steepness of gradient.

Inasmuch as the plenums 19 a, 19 b carry differential densities, theyare different sizes. In fact, the upper plenum 19 a may be thought of assimply a manifold 19 a feeding vapor at a comparatively larger specificvolume, lower specific density, into the closed channel 24. Similarly,the condensate 25 has a density almost 1,000 times greater than that ofthe vapor 27, corresponding to a specific volume of about one thousandthof the volume of the vapor 27. Thus, the manifold 19 b or plenum 19 breceiving condensate 25 from the closed panel 27 need not have the samevolumetric capacity as the upper manifold 19 a.

In general, droplets 130 form against the inside surface 106 of the wall26 in the panel 102. Droplets 130 tend to migrate downward and maylikewise coalesce into streams or rivulets running into the condensate25 collected at the bottom of the panel 102, resulting in condensatelevel 128 accumulating in panel 102. The result of condensing vapor 27on the inner surface 106 of the wall 26 of the closed channel 24, is avery high heat transfer rate on the order of 20 times greater than theheat transfer rate between liquids across a solid surface.

Thus, for example, the rate of heat transfer into the brine 22 from theouter surface 104 of the wall 26 is lower when merely resulting in heattransfer into the liquid brine 22. In contrast, the heat transfer rate,and thus the heat transfer coefficient upon nucleate boiling with bubble100 formation is comparatively about 20 times that rate, and correspondsto the condensation heat transfer rate on the inner surface 106 of thewall 26 in the panel 102 enclosing the closed channel 24.

Referring to FIG. 5, a chart 134 illustrates axes 136, 138. The heightaxis 136 illustrates the height from the outlet level 101 of the tank toabove the liquid level 100 including the plenum 58. Meanwhile, the TDSaxis or the total dissolved solids axis 138 illustrates theconcentration of total dissolved solids within the tank.

The curves 140 are gradients or profiles of concentration or density. Inthe illustration of FIG. 5, the location of the core 20 is shown indotted lines, as is the outer shape of a tank 30. The outer level of thetank 30 is illustrated, along with that of the core 20 in order to showthe response of the density profile 140 to the altitude or height 136along the height axis 136.

In the chart 134 of FIG. 5, the curves 140 represent concentrationsvarying from a minimum amount corresponding to the value on the TDS axis138 at its minimum value, at its intersection with the vertical axis 136or height axis 136. Meanwhile, at the liquid level 100, theconcentration and therefore the density of brine 23 in a tank 20 is at aminimum value of dissolved solids in an apparatus and method inaccordance with the invention.

However, in a mixed environment, one in which the brine 23 in a tank 30is completely mixed, a profile 140 reduces to a vertical line, having aconstant concentration and constant density throughout from the liquidlevel 100 to the outlet level 101. Thus, the concentration at the liquidlevel 100 is the same as that at the outlet concentration 142.

In an environment in which a gradient profile may be establishedideally, a static linear density profile may be established according tothe curve 140 b. In this situation, the concentration varies from aminimum value at the liquid level 100 and increases to a maximum outletconcentration 142 at the outlet level 102.

In order to establish the ideal gradient illustrated by the profile 140b, it would be necessary to maintain a continuous, and equal change inconcentration at substantially every level between the outlet level 101and the liquid level 100. This would require tremendous control, thoughit would also provide a predictable and useful and consistent gradientin the tank 30.

Experimental results in an actual apparatus 10 in accordance with theinvention is illustrated in the dynamic density gradient profile 140 c.In this profile 140 c is seen the change in the density gradient withinthe core region, as compared with the change indicated in the regionbelow the core. Between the liquid level, the bottom of the core 20, andthe outlet level 101, the normalized concentration difference, from thelowest concentration level at the liquid level continually increases tothe outlet level 101.

Accordingly, the outlet concentration level 142 of both profiles 140 band 140 c originate and terminate at equivalent points. In contrast,however, the density gradient curve 140 c is shown to stabilize in adifferent shape, in which most of the concentration increase occurswithin the altitude of the core 20, and very little change occurstherebelow. Thus, the region of the tank 30 below the core 20 may stillmaintain a gradient.

However, in these experiments not nearly so substantial a totaldifference as that achieved within the core 20 was observed. This isseen as indicating several facts, including the fact that the core 20 isthe region in which the open channels 22 are concentrating brine 23 byevaporating off vapor 27. Below the core, where no substantialvaporizing occurs, the difference in concentration is substantiallyless.

In reviewing the chart 134 of FIG. 5 in view of the phenomenaillustrated in FIG. 4, one may ascertain the degree of mixing occurringwithin the open channels 22, as opposed to elsewhere in the tank 30.Also, to the extent that the diffuser 68 of FIGS. 1-3 is located belowthe core 20, brine convection, or the brine density buoyant convection,will occur.

Likewise, for example, brine 23 incoming in the input flow 35 a islighter than any brine 23 within the tank 30. Thus, regardless of thevelocity with which the flow 35 a is introduced into the tank 30, itwill immediately begin to rise through the core 20, or anywhere elsewithin the tank 30 that it is introduced.

Accordingly, the brine buoyance plume created by the inlet brine flow 35a will rise toward the liquid level 100, exchanging momentum, massdensity, and heat with the surrounding brine 23 through which it passes.The dynamic density gradient profile 140 c therefore illustrates thatthe actual value of concentration or density within the tank 30 isneither the ideal static linear density profile 140 b, nor is it themixed non-gradient 140 a.

Thus, the dynamic density profile 140 c (gradient 140 c) is very usefulin the control and stabilization of a system 10 in accordance with theinvention. Of course, the ideal static linear density gradient 140 bwould be very useful but difficult to achieve, maintain, or both.However, experiments at this point demonstrate that moving away from themixed, non-gradient condition illustrated in the curve 140 a can beachieved, are easily maintained, and provide very useful results.

Referring to FIG. 6, a chart 145 illustrates curves 146 of an increasein total dissolved solids (TDS) as a function of the feed concentrationthereof. The formula 148 illustrates a normalized total dissolved solidsincrease represented by each of the curves 146. The curve 146 arepresents the increase in total dissolved solids in the brine 23 in thetank 30 at the comparatively minimum feed concentration of dissolvedsolids in experiments with the apparatus 10 in accordance with theinvention.

In contrast, the curve 146 e illustrates the increase in the normalizedtotal dissolved solids content in the brine 23 of the tank 30 at thecomparatively highest input concentration of dissolved solids in theexperiments. The height axis 136, as in FIG. 5, again measures from theoutlet level 101 in the tank 30, or of the tank 30 up to above theliquid level 100.

The liquid level 100 is the maximum height at which a general quantityof liquid brine 23 exists in the tank 30. Accordingly, only the plenum58, holding vapor 27, exists immediately above the liquid level 100.Thus, the dissolved solids content has a value 150 at the liquid level100. In the experimental system 10 in accordance with the invention, thelowest concentration of dissolved solids occurs at the liquid level 100.Thus, all values measured along the axis 138 are normalized against thatminimum concentration of dissolved solids 150.

The shape of the curves 146 reflects the change in rate of concentrationincrease with depth toward the outlet level 101. Thus, curves 146 b, 146c, 146 d reflect intermediate input TDS curves within the family ofcurves 146. The experimental data is contained in curves 146 a, 146 e.However, the consistent curvature obtained through multiple experimentsillustrates that the concentration profile and gradient within the tank30 are independent from the output TDS.

For example, the curve 146 a corresponds to input feed concentrations of50,000 parts per million as well as feed concentrations of 100,000 partsper million (ppm). Likewise, the curve 146 e represents tankconcentrations of 100,000 ppm and 200,000 ppm output brineconcentrations. However, the input dissolved solids concentration 146,when closer to the outlet concentration of dissolved solids, appears tohave less effect on mixing.

Likewise, the larger the discrepancy between the concentration at theinlet flow 35 a compared to the outlet brine flow 35 c shows a tendencyof the more concentrated brine in a tank 30 to rapidly dampen the effecton concentration by the incoming flow 35 a. Thus, as the input TDSincreases, the curve 146 moves from the curve 146 a toward the curve 146e.

Meanwhile, minimum and maximum output concentrations of dissolved solidsboth result in the curve 146 a. Thus, the normalized TDS increase isindependent from the output concentration of total dissolved solids atthe outlet concentration 152 at the outlet level 101 in the tank 30.

The curve 146 a corresponds to four sets of experimental data. Twoexperiments involved vapor recompression in an apparatus in accordancewith the invention at a 50,000 ppm of brine input into a tank 30. In onepair of experiments, the output brine concentration was near or at200,000 parts per million, the other 100,000 parts per million.Meanwhile, the curve 146 e corresponds to two experiments in which theoutput TDS concentration was 200,000 parts per million. The input feedrate was 100,000 parts per million in each of those experiments, and theoutputs were 180,000 parts per million and 200,000 parts per million,respectively.

Referring to FIG. 7A, a chart 154 illustrates a distribution oftemperature measured along the axis 156 against a height measured alongthe axis 136. In the chart 154, the average tank temperature 158 isillustrated at various positions, including the value of T1 or firsttemperature identified by the line 158 a, and a second temperature or T2at the line 158 b. Here, the curve 160 reflects the saturationtemperature in a stratified concentration profile of the tank 30.

The curve 162 illustrates the saturation temperature of a mixed brine 23in a tank 30. The difference between these curves 160 and 162 reflectsthe difference in saturation temperature as a function of stratifiedbrine concentration versus completely mixed brine in accordance withRaoult's Law, illustrated in FIG. 182. Both illustrate changes insaturation pressure with depth and density. Therefore, the curves 160,162 accommodate the depth difference at various locations within thetank 30.

Reference to FIGS. 7A-7E are best understood when viewed together. FIG.7A is a chart 154 illustrating saturation temperature differencesbetween a saturation temperature in a stratified tank (curve 160), whichis not a line, but rather a non-linear curve; the saturation temperaturecurve 162 describes a completely mixed tank 30. Thus, these two curves160, 162 correspond to the dynamic density profile curve 140 c of FIG. 5and the mixed non-gradient curve 140 a of FIG. 5, respectively.

The difference between the two curves 160, 162 is best understood byreference to Raoult's Law 182 described in FIG. 7B. Here the equationstates that the change in saturation temperature within a brine is equalto the product of the ionic constant corresponding to the chemicalconstituents making up the brine, with the ebullioscopic constantcorresponding to the units of degrees celsius times kilograms divided bymoles for water.

Similarly, the Clausius-Clapeyron equation 184 describes the rate ofchange of pressure with temperature according to the dependents on thelatent heat of vaporization divided by the temperature and the change inspecific volume (volume per unit mass). This equation may be written inseveral forms including one that indicates the change in pressure isequal to the pressure within the bulk fluid times a power of the naturallog. In this last embodiment, the coefficient ‘m’ is at best isolated asthe lower version of the equation 184 in FIG. 7C.

Thus, Raoult's Law governs the change in saturation temperature due tothe impurities within a liquid. The Clausius-Clapeyron equationcorresponds to the change in pressure as a function of temperature dueto compression of a vapor.

FIG. 7D illustrated Dalton's Law 186, sometimes referred to Dalton's Lawof Partial Pressures 186. Here, pressure within any volume is equal tothe fraction of that volume occupied by any particular vapor, usually anidealized gas, multiplied by the vapor pressure of that gas. Thus, thepressure in the plenum 58 is a combination of the partial pressures ofall the evaporated vapors 27 existing therein.

Referring to FIG. 7E Henry's Law 188 describes the relationship betweenconcentration of a solute (dissolved gas) dissolved in a solvent.Accordingly, the concentration of a particularly species designated bythe lower case letter ‘i’ is a function of the partial pressure or vaporpressure of that constituent in a volume divided by the Henry's Lawconstant.

Thus, Henry's Law 188 describes how much of a supposedly non-condensablegas is actually absorbed. Henry's Law also applies to other condensablegasses.

Therefore, when considering FIG. 7A, the saturation temperature withinthe tank 30 corresponds to a saturation pressure at any point (depth)within the tank 30. However, the saturation pressure varies with theconstituents dissolved in the brine, the volatile ions thereof, and thedepth at which one is observing temperature, pressure, and so forth, inaccordance with the foregoing equations.

Still referring to FIG. 7A, while continuing to refer generally to FIGS.1-12, the T1 and T2 average tank temperatures 158 a and 158 b merelyserve as points of reference. The effects of the curves 160, 162 applyat any particular location or depth within the tank 30. Accordingly, thetank temperature 158 is significant to a local effect on the saturationtemperature required to boil liquid to vapor 27 in the channel 22. Thus,the significance of the temperatures 158 a, 158 b is actually theirrelationship to the localized saturation temperature as given by curves160 and 162.

Effectively, the curve 162 is a calculated value corresponding to thesaturation temperature of the brine 23 in a fully mixed tank 30. Thus,the brine 23 corresponding to the curve 162 is fully mixed andcorresponds to the profile 140 a as illustrated in FIG. 5 andillustrates the absence of a profile or gradient.

At a tank temperature 158 a, the saturation temperature 162 correspondsto boiling liquid level 100 or a boiling surface point 164. Remaining ina mixed condition and descending from the liquid level 100 down towardthe outlet level 101, the saturation temperature 162 rises to a maximumof 156. This rise is due to the head level or height of the liquidcolumn above any particular location along the curve 162.

In this example, the surface boiling point 164 is at the surface exactlybecause there is no submersion below the liquid level 100, so thesaturation temperature 162, by the definition of saturation temperature,occurs at the boiling surface 164. In this example, the saturationtemperature curve 162 takes into account Raoult's Law 182 and its effecton the boiling temperature 162.

If the tank temperature is raised from the value 158 a to a highertemperature 158 b, then the same head height is imposed by the liquidlevel 100. Thus, the new boiling point 166 corresponds to surfaceboiling into the plenum 58, by the brine at the temperature value 158 b.Accordingly, if the temperature profile 162 or temperature curve 162were shifted to the right, corresponding to the increased temperature158 b, the curve 162 would only go through the point 166 if thesaturation pressure in the plenum 58 also rose to the appropriatesaturation pressure.

If the saturation pressure in the plenum 58 does not rise, then theregion between the liquid level 100 corresponding to point 166, and theheight along the axis 136 corresponding to the point 168 will all beboiling. In other words, core nucleate boiling would occur in the uppercore region of 176.

Nevertheless, in another example, one may think of the tank 30 being atthe average temperature 158 b and having the compressor 50 draw down thevapor 27 in the plenum 58. This would result in the drop of thesaturation pressure. Accordingly, having the plenum 58 at the saturationpressure corresponding the curve 162, while the average tank temperatureis at 158 b, the core region 176, between the surface point 166 and thepoint 168 on the curve 162, boils generally throughout.

The curve 160 represents the saturation temperature existing in the adynamic density profile or gradient 140 c in a tank 30. The curve 160intersects the tank average temperature 158 a at a point 170, acondition wherein the saturation temperature 160 within the tank 30 isexactly at the tank average temperature. Likewise, the point 172corresponds to the intersection of the saturation temperature curve 160and the elevated tank average temperature 158 b.

These two tank temperatures 158 a, 158 b are illustrated as constantthroughout the altitude of a tank 30 and are used merely by way ofexample. With a dynamic density profile 140 c (see FIG. 5) thestratification within the tank 30 may create any one of a variety oftemperature profiles. It is also possible to have a non-constanttemperature throughout the height of the tank 30. In other embodimentsit may be possible to have reverse gradients in which the hottesttemperature is at the bottom of the tank.

Again, anytime the localized saturation temperature 160, or 162 is belowa localized temperature 158 a, 158 b or the like, the brine 23 in thetank at that location will be in boiling mode.

In FIG. 7A, assume that the pressure in the plenum 58 is always at thesame, constant value throughout the following discussion. In the chart154, one may select a temperature 158 a within the tank 30.

Now, consider the saturation temperature curve 160 occurring with agradient in accordance with the invention and represents the dynamicdensity profile 140 c of FIG. 5 due to stratification of the brine 23 inthe tank 30. The intersection of this curve 160 intersects the surface100 not at the point 164, but at some point lower in temperature on axis156. In accordance with the foregoing discussion, boiling now begins aslow as the point 170, where the tank temperature 158 a intersects thesaturation pressure 160 of the brine gradient 140 c.

Given this condition existing at point 170, the entire region 174 abovepoint 170 is in a full boiling condition, with no additional energyintroduced. In the configuration represented by the chart 154, the fullymixed saturation temperature 162 is set to boil at the surface 100. Incontrast, at the same tank temperature 158 a, the stratified brine boilsin the entire region above the point 170. Thus, more of the core isinvolved in high heat transfer nucleate boiling, as compared with thatwhich would have been achieved in a completely mixed system.

Of course, if temperature were raised in order to engage more of thecore 20 in boiling, as would correspond to increasing the tanktemperature to the value 158 b, the point 166 is the temperature value158 b required in the tank.

However, in the stratified condition corresponding to the curve 160, thepoint 172 reflects the point above which full nucleate boiling occursthroughout the core 20 in the tank 30. Thus, the region 180 representsthe additional benefit, or the additional region of the core 20 in whichfull nucleate boiling is generalized in the core 20 as given by region178.

Just as the region 174 above the point 170 represents the portion of thecore 20 in full nucleate boiling when the tank average temperaturecorresponds to the value 158 a, this increased benefit continues at allpoints along the curve 160. Regardless of the depth of the region 176may be, in a fully mixed tank corresponding the saturation temperaturecurve 162, the stratified saturation temperature curve 160 alwaysprovides an improved performance represented by region 174, 180, or byother corresponding differences between the two curves 160, 162.

This benefit may be realized in one of several alternative ways, such asthe ability to run the system 10 at a reduced temperature for the sameperformance. Alternatively, the work done by the compressor 50 may bereduced due to the decreased demands on the saturation pressure in theplenum 58 above the liquid level 100.

Referring to FIG. 8, an experimental system 10 was configured with ahousing 12 having a motor generator system. Ultimately, an auxiliaryheater relying on line power was also included. The tank 30 was set upwith a core 20 placed therein connected to an upper, vapor manifold 19a, and a lower, liquid condensate manifold 19 b. The core 20 includedopen channels 26 in liquid communication with the surrounding region ofthe tank 30, while the closed channels 24 were sealed away from the tankbrine 23.

A plenum 58 above the core 20 accumulated vapors boiling from the openchannels 22 of the core 20. A mist eliminator 54 (not seen in FIG. 8)was positioned within the plenum 58. Meanwhile, a heat exchanger 15 wasinstalled, but was not used in the experiments reported in FIGS. 3-7E.The conduits 18 conducted vapor from the plenum 58 to the compressor 50,which then passed those vapors at an increased pressure into the vaporplenum 19 a or manifold 19 a.

The manifold 19 a distributed the vapors 27 into the closed channels 24of the panels 102 for condensation. Condensate 25 exited the closedchannels 24 through the bottom manifold 19 b as condensate. Ultimately,after holding in a reservoir 43 the distillate or condensate 25 from theclosed channels 24 was eventually passed on to a distillate tank.

Above the core 20, a plenum 58 was arranged, and contained a misteliminator 54. After passing through the mist eliminator, the vapor 27in the plenum 58 was passed by a heat exchanger 15 which was not activeduring the experiments reported in FIGS. 4-7E. Instead, the vapor 27passed on into the conduit 18 toward the compressor 50. The compressor50 increased the pressure, and the temperature in the vapor, passing thevapor at this increased temperature and pressure of saturation back intothe manifold 19 a at the top of the core 20.

The manifold 19 a passed the vapors into the closed channels 24 of thepanels 102, where it was condensed by discharging the latent heat ofvaporization into the surrounding brine 23 in the open channels 22 ofthe tank 30.

The condensate 25 was then passed from the closed channels 24 into themanifold 19 b at the bottom of the core 20, and ultimately dischargedthrough a reservoir 43 into a heat recovery system 47 (as illustrated inFIG. 1) to a distillate tank 42, which are not shown in FIG. 8.

Meanwhile, the system was instrumented with sensors 72 near the centralgeography of the core 20. Heaters were positioned along the walls 31 ofthe tank 30. The motor 17 driving the compressor 50 was controlledthrough a control system that would vary current to the motor 17, thusaltering the velocity, throughput, and volumetric flow rate of thecompressor 50.

The sensors 72 were placed in the open channel 22 at the center of thecore 20. Likewise, sensors 72 were placed along the walls asillustrated, and distributed schematically in FIG. 1. Sensors 72 wereconfigured to detect temperature and concentration within the brine 23of the tank 20, in the core, and near the wall 31. Other temperaturesand pressures were detected in the plenum 58, the conduits 18 on theupstream side and downside stream side of the compressor 50, and soforth. Various experiments were run on the apparatus 10 of FIG. 8 in thedevelopment of the data of FIG. 6.

Referring to FIG. 9, a mass balance reflects the input of the flow rates35 a introduced into the tank 20 and the output flows 35 c exiting thebrine heat exchanger 36, as well as the quantities of distillate 25 orcondensate 25 passed through the distillate heat exchanger 44 to thedistillate tank 42.

The experiments contributing to the charts 134, 145 of FIGS. 5 and 6respectively correspond to the data obtained at the experimentalconditions 194 a and 194 b, the conditions at location 194 c and 194 d,and the conditions at 194 e, 194 f. The conditions 194 a, 194 bcorrespond to an input feed of 50,000 parts per million. The outputcorresponds to a brine concentration of 100,000 parts per million intotal dissolved solids exiting the tank 30.

Meanwhile, the conditions 194 c and 194 d correspond to an input brineconcentration of 50,000 parts per million and an output concentration of200,000 parts per million. Likewise, the conditions 194 e and 194 fcorrespond to an input concentration of 100,000 parts per million withan output concentration of 180,000 parts per million and 200,000 partsper million, respectively.

The data conditions of the table 190 of FIG. 9 correspond to a constantoutput of distillate 25 of 100 barrels (168 liters) per day.Notwithstanding the output brine concentration for the conditions 194 eand 194 f were not only set at 200,000, the conditions under experiment194 e were set at an output brine concentration of 180,000 parts permillion. Referring to FIG. 10, the experiments corresponding to theconditions 194 of FIG. 9 were implemented in the system 10 of FIG. 8.The chart of FIG. 10 plots the normalized increase in total dissolvedsolids, according to the formula 148 illustrated thereon through the sixexperiments 194 or the six sets of experimental conditions 194.

The normalized concentration of dissolved solids is illustrated on theTDS axis 138 and plotted against the height from the outlet level 101 upto the liquid level 100 in the tank 30. The region above the liquid line100 or liquid level 100 corresponds to the location just above the core20, which was completely immersed in brine 23.

The total dissolved solids value 150 at the top of the brine 23 or theliquid level 100 is normalized, or used as the normalization value, forall the flows. Accordingly, the normalized increase in total dissolvedsolids is expressed as a fraction above the concentration value at theliquid level 100.

As can be seen from the chart of FIG. 10, the curves 195, 196, 197reflect the fit of data obtained. The curve 195 corresponds to the fitof data to experiment 194 a and experiment 194 b. The curve 196 is a fitto the experiment based on the conditions 194 c and 194 d Likewise, thecurve 197 is fit to the data corresponding to the conditions 194 e and194 f.

The curves 195, 196, 197 correspond to the curves 186 of FIG. 6.Meanwhile, F135 a and F235 a are illustrated by their relative heightalong the height axis 136. One may note that the brine buoyancy plumeeffect was significant in altering the total dissolved solids within thegradient in the tank 30. Additional information is also available fromthe raw data charts corresponding to the experiments 194 in FIG. 10.

For example, at the location where the feed flows 35 a were introducedinto the experimental tank 30, no diffuser 68 was available.Accordingly, the flows 35 were introduced as several pipes eachinjecting a horizontal jet of the input feed brine 35 a from the feedtank 32. Both momentum in the horizontal direction, and the buoyancyforces vertically affected the integration of the input flow 35 a intothe brine 23 of the tank 30.

Moreover, the experiment conditions 194 c and 194 d were intended tocorrespond to an output brine concentration of 200,000 parts permillion. In contrast, the conditions 194 a, 194 b were intended tocorrespond to an output brine concentration of 100,000 parts permillion. The effect of brine concentration in the input flow 35 a issignificant. Where the brine concentration in the tank 30 was four timesthat of the incoming brine flow 35 a, the tank brine 23 very quicklyrectified the concentration of the incoming flow 35 a. Above thelocation of the feeds 35 a, the curves 195, 196, 197 match quite closelythe raw data.

However, in the vicinity of the incoming flows 35 a, the disruptiveeffect of mixing is seen in the reduction of concentration below thecurves 195, 196, 197. This suggests that the system 10 is very robust.For example, the curves 195, 196, 197 are highly dependent on theincoming concentration of the incoming flow 35 a and exhibit virtuallyno dependence on the output concentration.

Thus, the dynamic density profile 140 c (see FIG. 5) as detailed by thecurves 146 (see FIG. 6) may be relied upon to provide a stable,predictable output condition for the system 10. The heat input, and workinto the compressor 50, may be adjusted to accommodate the incoming feedflow 35 a to reach the output desire. Significantly, the output resultis not in substantial question.

The data of FIG. 10 also substantiate the robust performance andresilience of the gradient in the tank 30 in the face of wide variationsin the incoming brine concentration. This is particularly significant inactual production facilities where the incoming brine flow 35 a may varyas fracture water, production brine, or the like. These data demonstratethat the output and control of the system 10 need not be subject to sucharbitrary inputs.

Referring to FIG. 11, a chart 198 illustrates the effect on temperaturealong the temperature axis 150 at various levels of depth illustrated onthe axis 136. Temperatures are not normalized to a non-dimensional formas with other figures. Here, the saturation temperature curves 160, 162correspond to those of FIG. 7A. These values reflect actual data fromthe experiments 194 corresponding to FIGS. 9-10. Here, the point 199represents the saturation temperature at the surface 100 or the liquidlevel 100 in the tank 30. The conditions at the point 199 constitute thesaturation temperature at the liquid level 100 for a fully mixed tank.This corresponds to the conditions of the curve 162.

Similarly, the point 200 represents a saturation temperature at thepressure in the plenum 58 above the liquid level 100. Likewise,saturation conditions at the liquid level 100 along the curve 162, thepoint 200 corresponds to the curve 160 of a saturation temperatureexisting at the pressure in the plenum 58 for a dynamic gradientconfiguration of FIGS. 9-10.

The empirical data of FIG. 11 confirm the operational characteristicsdiscussed with respect to FIG. 7A. For example, the region 176corresponds to the description of the region 176 with respect to FIG.7A. Likewise, the region 178. Similarly, the region 180 of FIG. 7A isthe difference between the depth of the region 176 and the region 178.

This represents the advantage in heat transfer area and greatlymultiplied heat transfer coefficient in the region of nucleate boilingin the core. The core 20 is illustrated by dotted line surrounding aregion reflecting the actual depth and position of the core 20 in thetank 30 during the experiments 194.

Referring to FIG. 12, while continuing to refer generally to FIGS. 1-12,a process 202 for controlling an apparatus 10 in accordance with theinvention may have several levels of control. For example, a zero level203 represents balancing mass by a continuous process of tracking andadjusting the levels of liquid in the tank 30 and in the distillatereservoir 48. These are directly observable and adjustable timely byconventional measurement and control techniques.

Meanwhile, a level one control 204 as well as a level two control 205and a level three control 206 are illustrated. Level one control 204involves control of the work done by the compressor 50. In theillustrated process 202, level one is seen as intervening 204 in theoperation of the process 202 operating in the system 10.

A principal mechanism for control is reducing 211 or otherwise changing211 the work done by the compressor 50 in removing vapor 27 from theplenum 58. Typically, the reducing 211 operation corresponds to acontrol intervention 204 initiated in response to an undesired rise inthe liquid level of the reservoir 43 containing distillate. A change 211in the work done by the compressor 50 causes a response 212 in thesystem 10. For example, reducing 211 the work done by the compressor 50causes a rising pressure in the plenum 58. Likewise, a decreasing massflow rate will result through the compressor and out of the plenum 58.This is somewhat counterintuitive.

For example, decreasing 211 or reducing 211 the work done by thecompressor backs up pressure in the plenum 58, causing core boiling todecrease and decreasing the distillate temperature and saturationpressure. These system responses 212 result in a readjustment of theoperation point of the system 10. Specifically this alters the pressurein the plenum 58, thereby forcing a readjustment of saturation pressureand saturation temperature in the brine 23.

As a practical matter, the process 202 illustrated in FIG. 12 is anexample of controlling the system 10. Accordingly, the most responsiveelement for controlling operation of the apparatus 10 or system 10 isthe level one control 204.

Level two control 205, or intervening 205 in the level two controlscheme, involves adjusting 213 the auxiliary heat provided by theauxiliary heater 70. In this example, adjusting 213 is embodied indecreasing auxiliary heat output by the auxiliary heater 70. This may bedone by controlling the heater 70 or the auxiliary heat source 46.

By decreasing 213 auxiliary heat, intervening 205 follows the more rapidand responsive 211 of the intervention 204. However, in intervening 205at level two control, the decrease 213 in auxiliary heat results in amuch slower response of the system. This includes a decreasingtemperature in the tank, decreasing mass flow rate of the distillate 25,and decreasing core boiling.

The temperature 158 a is moved to the left in FIG. 11. However, anexcursion away from the curve 162 will typically occur as a systemresponse 212. By decreasing 213 the auxiliary heat, the temperature line158 a moves to the left, corresponding to a net cooling of the tank 30.The result of moving the line 158 a to the left is a decrease in theregion 176 and an increase of the region 180 between the regions 176,178.

Perhaps the most significant effect of moving the temperature ordecreasing 213 the heat with its corresponding decrease in thetemperature 158 a is to reduce the region 178, by shifting the positionof the intersection point 172 at which the temperature line 158 aintersects the curve 160. Thus, less of the core 20 is involved inboiling. Accordingly, a decreasing mass flow rate and a decreasing coreboiling will occur as system responses 214 in accordance with FIG. 12.

Intervening 206 at the level three control, as described in reference toFIG. 2B, may involve processing 215 by a computer processor in order toprovide a predictive trim to the other levels of control. Accordingly,the controller 84 may receive signals from any or all of the sensors 72.It may provide instructions commanding 216 modifications to the work,heat, or, optionally, mass flow rates in the system.

Commanding 216 an alteration to these independent control variables mayresult in alteration of the dependent variables. Accordingly, feeding217 data back or providing 217 feedback of values of pressure,temperature, mass flow rate, concentration, or the like will reflect thedependent variables on which the independent variables of work and heatare controlling.

In certain embodiments of an apparatus in accordance with the invention,and a method 202 in accordance therewith, intervening 206 at level threecontrol may involve numerical methods implemented to predict and stableystep the commands 216 to set points that are expected, projected,predicted, or otherwise calculated to secure proper values of thedependent variables of pressure, temperature, mass flow rates, andconcentration at any particular point within the system 10.

Upon the intervening 206, the system, and particularly the controller84, may render a decision 207 on whether or not the system 10 is stable.If the system 10 is stable, continuing intervention 206 of the levelthree control may involve trimming in a predictive fashion anyindependent variable necessary. However, if the decision 207 is that thesystem 10 does not appear to be entirely stable, the process 202 mayadvance to detecting 209 an event 208 responsible.

For example, if the system 10 does not appear stable, certain events 208are occurring that may be the effect of atmospheric pressure, change inconcentration in the input flows 35 a, or the like. Any drifting of thesystem 10 away from the predictive trim control of the intervention 206will typically be a result of an event 208 altering the condition of thesystem 10.

Accordingly, detecting 209 the consequences will typically involvefeedback 217 from sensors of pressure, temperature, mass flow rate,concentration, a combination thereof, or the relationships therebetween.For example, the system may encounter a decrease in atmospheric pressureLikewise, the system 10 may detect an increase in mass flow rate ofdistillate. In this example, these changes will be detected by sensor 72and reported back to the controller 84 as data inputs, reflectingconsequences of the event 208. Following detecting 209 theseconsequences, activation 210 of the control through the controller 84 isappropriate. The level zero control 203 is left out of the control loopof the process 202 for purposes of illustration. The level zero controlinvolves control of parameters that can easily be observed, controlled,and immediately affected. Adding liquid through adjustment of the rateof flow through a pump 76 b will result in increased flow 35 a into thetank 30. Likewise, an increase in the speed of a pump 76 d may occur byslaving the control for the pump 76 d to the volumetric flow rate,speed, current, or other control mechanism of the pump 76 b.

In contrast, determining exactly how much heat should be added to theauxiliary heater 70 is not necessarily an intuitive process and iscertainly not directly observable nor controllable manually or by asimple feedback sensor. The time of response for the temperature in thecore 20 or the tank 30 is comparatively long (e.g., 4.6 hours), and theresponsiveness of the compressor 50 is so fast (seconds), that ameasurement on a sensor 72 d in the plenum 58 does not necessarilyprovide an obvious direction for intervention 204, 205 at levels one ortwo, respectively.

The level zero control may also be trimmed by the intervention 206 atlevel three. Slight adjustments may be made for losses, miscalculations,calibrations, and the like. However, as a practical matter, the levelzero control need not be included in the control loop of the process202.

One way to consider the intervention 206 at level three control is interms of predicting what control parameters should be adjusted, and inwhich direction they should be adjusted, based on an algorithmicprediction of where the system needs to move, so to speak. Thus, ratherthan simply tracking a dependent variable and adjusting a singleindependent variable, the predictive trim control intervention 206 isvery much a sophisticated function reflecting the sophisticatedinterrelationships between heat and mass transport within the system 10and among its many components.

Another way to think of the control process 202 is with zero level ofcontrol 203 maintaining a mass balance according to the first law ofthermodynamics. The mass within a system must be the mass flowing inless the mass flowing out.

Likewise, the intervention 204 at the level one control represents anenergy balance. That is, modifying 211 the work being input as theprimary energy source in the operation of the system 10. That is, heatfrom the auxiliary heater 70 does not operate the system 10. Power orwork by the compressor 50 operates the system 10 and makes up the energylosses required by the thermodynamic cycle thereof.

Intervention 205 at the level two control actually is not a principlecontrol of the system 10. Rather, intervening 205 by adjusting 213auxiliary heat is a mechanism for adjusting the operational parametersof the system 10 in accordance with outside effects.

For example, if a storm front rolls in, then atmospheric pressure willdecrease. Since the tank 30 is not sealed as a pressure vessel, thepressure in the plenum 58 may track ambient or atmospheric pressure. Apressure drop in the plenum 58 may easily be larger than the temperaturedifferential being controlled above atmospheric in the plenum 58.

Thus, intervening 205 at level two involves adjusting the temperature ofthe tank brine 23 in order to adjust the overall operation of the system10 to changing outside conditions. Intervening 205 at level two may beresetting the system to adjust to a new steady state of operation withinits environment. Environment cannot be controlled by the system. Rather,the system 10 must adjust to its environment and does so by theintervention 205. Therefore, intervention 205 is prospective to theextent that it is initiated as a result of intervening 204 at level one.However, it may still be directed to readjusting the parameters of thesystem 10, so the system 10 may arrive timely at a new and futureequilibrium and steady state condition.

Thus, intervening 206 at level three of control is almost entirelypredictive. All the lower levels of control are considered and theoperational characteristics are modeled in order to determine thenonobvious set points to which independent variables must be set.Dependent variables thereby arrive at their steady state and properconditions, in the most effective and timely manner.

Thus, each of the levels including intervention 203 at level zero,intervention 204 at level one, intervention 205 at level two, andintervention 206 at level three abstract the control by the controller84. Control moves further from direct values of measurable parameters,and away from direct response to current conditions.

Another way to think of this control process 202 is with level zeroeffectively independent closed loop control of a mass balance directly,direct control of the value. Intervening 204 at level one is assertingcontrol over an independent variable directly, and the dependentvariable indirectly, by a change in work.

Meanwhile, intervening 205 at level two involves addressing theparameters that affect the rate of change and the direction of change,rather than affecting the observed variable itself. Finally, intervening206 at level three involves predicting rates of change of rates ofchange of parameters to be controlled.

The present invention may be embodied in other specific forms withoutdeparting from its fundamental functions or essential characteristics.The described embodiments are to be considered in all respects only asillustrative, and not restrictive. All changes which come within themeaning and range of equivalency of the illustrative embodiments are tobe embraced within their scope.

Wherefore, we claim:
 1. A method of removing a contaminant from acarrier, the method comprising: selecting a liquid operating as acarrier; selecting a contaminant found in the carrier to be a targetedcontaminant; providing a circuit comprising a vapor re-compression cyclehaving a first region containing nucleate boiling; introducing into thecircuit the carrier containing the contaminant; establishing in thefirst region a concentration gradient of the contaminant; controllingthe first region by manipulation of the concentration gradient; andreturning a condensate comprising the carrier containing less than apre-determined concentration of the contaminant.
 2. The method of claim1, wherein: the method further comprises returning from the first regiona brine; at least one of the condensate exiting the cycle and a vaporwithin the cycle is substantially devoid of the contaminant; andproviding from one of the condensate, vapor, and brine a feedstock for asubsequent unit operation.
 3. The method of claim 2, wherein thefeedstock provides at least one of: a precursor for a chemical reactionin the subsequent unit operation; a fluid having independent economicvalue in a first market; a constituent, derivable from the fluid, andhaving independent value in a second market; the fluid reusable directlyfor recycling in a source process providing the carrier to the circuit;an increased operational efficiency for a disposition process disposingof the feedstock; reduction of environmental impact of the contaminant;and improvement in a compliance process in satisfaction of at least oneof a governmental regulation, industry standard, health standard, safetystandard, and a contractual requirement.
 4. The method of claim 3,wherein the subsequent unit operation is selected from synthesis ofhydrochloric acid, synthesis of another acid, hydrolysis, electrolysis,an ion exchange operation; an osmotic separation process, a vaporizationseparation process, coagulation, other chemical separation process,centrifugation, filtration, sluicing, settling, flocculation, andanother mechanical separation process, microwave separation, anothermicrowave treatment, re-injection into a well, a geologic fracturingoperation, blending with another material, reacting chemically withanother material.
 5. The method of claim 4, wherein the contaminantcomprises at least one of a dissolved solid, suspended solid,hydrocarbon, salt, heavy metal, other metal, volatile organic compound,other organic compound, oxide of nitrogen, other nitrogenous compound,alcohol, oxide of sulfur, other sulfurous compound, calcium compound,halide, other ion, acid, and base.
 6. The method of claim 5, whereinproviding the circuit comprises providing modules for effecting thecircuit.
 7. The method of claim 6, wherein the method further comprises:providing a specification defining a system having a plurality of themodules, each module thereof implementing an instance of the circuit,and containing the circuit unit operations corresponding thereto; sizingthe system to match a source of the contaminant; and providing theplurality of modules, operating together as the system, the number ofmodules therein being selected based on an output from the source. 8.The method of claim 6, wherein the method further comprises: providing arequirement, pre-determined and corresponding to a source of thecontaminant; defining a system having a plurality of the modules, eachmodule thereof having a type and implementing at least one functionspecified by the requirement; selecting a value representing a number ofmodules of each type to be included in the system as selectedcomponents; configuring the system by connecting the selectedcomponents.
 9. The method of claim 6, wherein each module of the modulesis mounted on a connecting structure and sized to be commerciallytransportable in accordance with transportation limitations provided byregulation.
 10. The method of claim 9, further comprising assembling afacility in a pre-determined configuration by connecting the connectingstructures to one another and rendering the modules interoperable.
 11. Amethod of separating out a material contained in a liquid, the methodcomprising: providing from a source, a liquid operating as a carriercontaining a material targeted for separation from the liquid; providinga circuit constituting a vapor re-compression cycle having a firstregion containing nucleate boiling and a second region containing vaporcondensation; introducing into the circuit the liquid; establishing inthe first region a concentration gradient of the material in the liquid;controlling the nucleate boiling by manipulation of the concentrationgradient.
 12. The method of claim 11, further comprising: returning fromthe second region a condensate comprising the liquid containing lessthan a pre-determined concentration of the contaminant; and returningfrom the first region a brine.
 13. The method of claim 12, furthercomprising: returning from the circuit at least one of a condensate, aportion of the vapor, and a brine, wherein at least one thereof containsthe material, and at least one other thereof is substantially devoid ofthe material.
 14. The method of claim 11, further comprising: providinga feedstock constituted by at least one of a condensate separated fromthe material, a vapor separated from the material, a brine into whichthe material has been concentrated, and a solid comprising the material;and providing the feedstock to a subsequent unit operation.
 15. Themethod of claim 14, wherein the feedstock provides at least one of aprecursor for a chemical reaction in the subsequent unit operation; afluid having independent economic value in a first market; aconstituent, derivable from the fluid, and having independent value in asecond market; the fluid reusable directly for recycling in a sourceprocess providing the carrier to the circuit; an increased operationalefficiency for a disposition process disposing of the feedstock;reduction of environmental impact of the contaminant; and improvement ina compliance process in satisfaction of at least one of a governmentalregulation, industry standard, health standard, safety standard, and acontractual requirement.
 16. The method of claim 14, wherein: thesubsequent unit operation is selected from synthesis of hydrochloricacid, synthesis of another acid, hydrolysis, electrolysis, an ionexchange operation; an osmotic separation process, a vaporizationseparation process, coagulation, other chemical separation process,centrifugation, filtration, sluicing, settling, flocculation, andanother mechanical separation process, microwave separation, anothermicrowave treatment, re-injection into a well, a geologic fracturingoperation, blending with another material, reacting chemically withanother material; and the material comprises at least one of a dissolvedsolid, suspended solid, hydrocarbon, salt, heavy metal, other metal,volatile organic compound, other organic compound, oxide of nitrogen,other nitrogenous compound, alcohol, oxide of sulfur, other sulfurouscompound, calcium compound, halide, other ion, acid, and base.
 17. Themethod of claim 11, wherein the method further comprises: providingmodules for effecting the circuit; providing a specification defining asystem having a plurality of the modules, each module thereofimplementing an instance of the circuit, and containing the circuit unitoperations corresponding thereto; sizing the system to match a source ofthe material; and providing the plurality of modules, operating togetheras the system, the number of modules therein being selected based on anoutput from the source.
 18. The method of claim 11, wherein the methodfurther comprises: providing modules for effecting the circuit;providing a requirement, pre-determined and corresponding to a source ofthe material; defining a system having a plurality of the modules, eachmodule thereof having a type and implementing at least one functionspecified by the requirement; selecting a value representing a number ofmodules of each type to be included in the system as selectedcomponents; configuring the system by connecting the selectedcomponents.
 19. A system comprising: a circuit for processing fluids byvapor re-compression, the circuit comprising an evaporation region; aworking fluid circulating through the circuit; a material containedwithin the working fluid and targeted for separation therefrom; anevaporator, controllable by an operator, located within the evaporationregion, and providing control of nucleate boiling by establishing andmanipulating a concentration gradient of the material in the evaporationregion.
 20. The system of claim 19, further comprising: modulesconstituting the circuit, wherein each module is mounted on a connectingstructure and sized to be commercially transportable in accordance withtransportation limitations provided by regulation; and the modules,being further connectable and interoperable in a pre-determinedconfiguration when the connecting structures are secured to one another.